


Gazing Abyss

by Kiar



Series: Undertale Beginnings [2]
Category: Undertale (Video Game)
Genre: Angst, Beginnings, Blood and Injury, Death, Explicit Language, Gaster Needs a Hug, Implied/Referenced Torture, Maybe a bit of fluff, Medical Experimentation, Needles, Prologue, So much angst, Time Travel
Language: English
Status: Completed
Published: 2017-07-13
Updated: 2018-02-27
Packaged: 2018-12-01 11:36:54
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 12
Words: 40,775
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11485596
Author URL: https://archiveofourown.org/users/Kiar/pseuds/Kiar
Summary: This story is a branch off of Bare Bones, taking place between Chapter 8 and 9. So if you haven't read up through Chapter 8, you should probably read that for some context, first.This story is Gaster-centric and focuses on his experiences when he first arrives in the Underground. It will deal with pain, magic, and a fair bit of bad science. Alphys will be a fairly major supporting character.Hope you enjoy.





	1. 6000 Feet Beyond Man and Time

**Author's Note:**

> I initially wasn't going to write this until I had a stronger idea of where the fic will end, but I had a really bad week and needed to get some frustration out of my system. And what better way to do this than torture a skeleton?
> 
> The story begins just after the Time Machine activates...

With the burst of lightning and its accompanying jolt that seized every muscle in his body, Gaster had enough time to register a single thought:

He’d been too slow.

Then it was pain and blinding light, and he lost the sensation of Sans’s hand in his own, and then even the light couldn’t be seen anymore because he was blind, well and truly. It was an absence of light, rather than a darkness. His senses had been stolen from him - sight, smell, sound, taste, touch - no, no not touch. He could still feel. He could feel _too much_.

Every nerve ending raw and exposed, every fiber of his being on fire and burning to the wick. Like rings of a tree he could feel the heat clawing inwards, eating him away in layers which crumbled to charcoal and sloughed off in waves of precious embers. His body - his life - leaving him with each new surge of blistering heat. And there was nothing he could do but endure.

The warmth that left him hung close, cocooning him in a glow of plasma. Gaster diminished and the cloud grew until he felt empty, empty of thoughts and emotions and anything that wasn’t the lingering awareness of pain. Yet somehow he could feel it was a moment of in-between - an eye of the hurricane - the breath held before the exhale. And it was in this crux that he felt… the other.

Someone else. A presence. Gaster was overcome by a strong instinct of intimate recognition, though the impression wouldn’t resolve any further into who - or what - the thing might be. It was watching him. Curious, and detached. Pitying, and amused. Regretful, and resigned.

Fractured.

Lost.

Gaster could almost see them. Not visibly, but with another sense - he could almost, _almost_ fit together those thoughts and feelings into an identity that he recognized, like overlaid lenses of a microscope. One last lens was all it would take to snap everything into focus, but it was then that the heat began to converge on him once more, and all thoughts of The Other were quick to evaporate.

The pressure was more than Gaster could take. It gripped him from every angle, straining against his skull while at once inside of it, threatening to tear him to pieces. The heat grew denser, hotter, squeezed tighter. Gaster could feel it shimmering throughout his body, rippling waves of inferno that pulsed through his bones and threatened to crack them open like logs in a fire.

It had become a core. A nuclear reactor. It was spitting ions and he was the heat-sink. His chest _burned_ and his bones strained. No, but it was _fusion_ , not fission - a star, roiling and new, lodged in his ribcage, burning with life and far too much energy for him to contain. Gaster buckled beneath the tension, searing cracks etching their way through his bones as he threatened to shatter. This was it. The tipping point. Just another moment, and then-

_Sensation._

Blessed cool air and solid ground, lights and sounds and smells. Gaster crumpled to the ground as he gave voice to his pain, letting out a ragged scream. Oh, _Lord,_ was he in pain, but he was also _alive_ , and out of whatever hellhole he’d just been dragged through. Gaster hissed as he curled his fingers into the mossy ground, finding the movement as painful as the coolness was soothing. White-hot threads of pain traced all across his body, spiking with every slight gesture, but it was bearable. It was nothing compared to what he’d just been through. He could push through this. He could endure.

Even so, he couldn’t stifle his next yelp of pain as he rolled onto his side. He lay that way for a long time, trying to move as little as possible and focus only on his breathing. After a while, the fire that flared through his chest and back with each breath died down into a more tolerable burn. It was only after some of the pain had subsided that he was able to gather his first lucid thoughts.

He’d made it through. The machine had _worked_. Well, perhaps not exactly as he had intended, but at this point he was willing to cling to any small victory he could get his hands on. Gaster had gone through one side of the spacetime machine and come out the other. _Where_ and _when_ he was, exactly, was something to be determined, but at least he’d managed not to end up a thousand feet above or below the surface. He also appeared to be in a breathable atmosphere - another plus. All things considered, he’d chalk this endeavor up as a scientific success. He couldn’t wait to see the look on Sans’s face when-

Gaster’s pride took an abrupt nosedive as the circumstances of the machine’s activation came suddenly back to him. Gaster’s eyes snapped open and he bolted upright, fire ripping through him once more as his injuries screamed in protest. The pain caused him to gasp and his head to spin, but he was in too much of a panic to slow down and let his body adjust. His vision was blurred and the muted lights stabbed painfully into his eyes, yet he still swung his head about in a frantic search of the area. He had to be nearby, he _had_ to be.

“Sans- _Agk-_ ” Gaster cut off mid call, overcome by a fit of coughs. They sounded wet, and each hack sent sharp lances of pain through his ribs and skull. Between the pain and frantic breathing, Gaster began to grow lightheaded. This time the vertigo was too much and Gaster overbalanced, managing to catch himself with an arm as he fell to his side. Blinding pain accompanied the action, stabbing up his arm and shoulder. Gaster’s coughs turned into choked gasps, and he quickly pulled his limb back towards him, cradling it to his chest. His other hand was raised to his mouth, ineffectively attempting to stifle the excruciating fit of coughs.

Through a daze of tears and dizziness, Gaster’s eyes finally managed to focus on something before him. It took his mind much longer to catch up, for the sight was so strange that at first he couldn’t even make sense of what he was looking at.

Gaster lowered his hand from his mouth, staring dumbly at his hand. It was like a scene from a horror movie - some macabre prop made out of plastic and food coloring.

Bones and blood.

A startled, painful laugh escaped Gaster’s mouth. _No wonder it hurts so much_ , he thought faintly. He laughed again, a staticy panic growing in the back of his mind. Oh. Oh, he was hurt much worse than he’d thought, wasn’t he? Gaster swayed as he tried to comprehend this, but his body was already shifting into a state of shock. _Defense mechanism_ , Gaster realized. To protect him from himself. That probably… that probably wasn’t a good thing.

Gaster tried to fight the instinct off, but another glimpse of his arm sent a strong wave of fear and nausea rolling through him. This was very bad. He… had to get help. He had to… do something.

A warm glow grew in Gaster’s chest as his mind spun and panic threatened to boil over. The heat seeped out and into his bones, once more alighting Gaster with fine traces of simmering pain. Gaster gasped and pressed his hands to his head, overloaded by all the stimulation and fear.

 _Calm, calm_ , he tried to will himself. He had to remain cognizant. Now was not the time to submit to emotions. He just needed to get help, and to not think about… about...

Gaster bent forward as he heaved a blood-flecked retch. The glow in his chest glared more intense in response, though Gaster hardly noticed as his mind hazed over. The pain suddenly seemed more distant. That was good. His limbs also felt distant, but so long as it didn’t hurt so much maybe he could try to walk.

Gaster sat up, but before he could stand his vision tilted, and he was still thinking about how curious this was as he crumpled back to the ground.

The image of a skeletal hand splattered with blood was the last thing to pass through Gaster’s mind before he lost consciousness.


	2. Will to Power

**Summary for the Chapter:**

> In which Gaster is in denial.

Consciousness came and went like a tide. There was movement and voices, but it was difficult to pay attention to either of them. Much easier to slip back into the warm apathy of sleep.

“...wrong with him?!”

“I-I don’t know! Hurry, j-just put him down here…”

Dull pain throbbed through his body as a jostling motion edged him towards wakefulness. Something solid pressed against his back, and then there was stillness once more. The voices were frantic, but Gaster couldn’t bring himself to care. He began to fade…

There was a period of blissful darkness.

Then pain unceremoniously wrenched him back. Gaster gasped as heat pulsed through his bones.

“...on’t stop! Not u-until the other healer gets here.”

“Yes, doctor.”

“Is he falling down?”

“No, I- I don’t- this isn’t like anything I’ve ever seen! Len, quick-”

“What the hell. Is this even _blood_? Why isn’t it dusting?”

“I-I don’t know. I don’t know!”

Gaster’s eyes cracked open to a blinding white glare of light. He hissed in a shaky breath, and his mind spiraled as it tried to associate words with the blurry shapes that surrounded him. Sensation was quickly returning, and with it a world of pain. Clumsily, he tried to turn his head.

“Hey, he’s awake!”

“The drugs, doctor-”

“Oh, th-thank goodness-”

“How are you even going to- oh.”

A sharp, precise pain lanced through the entirety of his being. Gaster cried out, and the pain shifted into a tension. There was a growing tightness, a strained pressure. Gaster raised a hand to fend off the intangible attack, his movements fuzzy and belated.

“What did you do?!”

“A sedative - he n-needs to stay still-”

“His magic, though! What’s it doing-”

“I-I don’t- oh no-”

The squeezing sensation on his body released, and Gaster gasped in a relieved breath.

“Is he falling down?”

“No, I- I don’t- this isn’t like anything I’ve ever seen! Len, quick-”

“What the hell. Is this even _blood_? Why isn’t it- oh shit, I think he’s awake!”

“What? Oh! S-sir, please stay still…”

This time when he opened his eyes the colors began to take on more definite forms. Between that and his slowly clearing mind, he was able to fit together a few cohesive observations.

He was laying down on a bed or gurney of some kind. There was a phosphorescent light overhead, and several figures leaning over his prone body. He was in a hospital, probably. And he also wasn’t dead. That was good.

“Doctor! His magic. These numbers…”

One of the figures pulled away.

“What? H-how? It was higher just a moment ago - oh, oh no-”

Gaster felt himself drifting off once more. The pain was receding, along with all other facets of sensation. The darkness was cool and numbing.

“What’s happening?”

“H-his soul- it’s- it’s crashing! I d-don’t know what-”

“Where’s the other healer?!”

“She’s coming-”

“I c-can’t stop it!” The voices were growing more distant. “I can’t stop it…”

 

\---

 

When Gaster next awoke everything was still and quiet. The pain was still there, faintly throbbing, but without the feverish heat from before. His mind moved between ideas more clearly; it seemed his torpor had passed. Gaster exhaled slowly and carefully, all too aware of the wounds that twinged at the compression of every breath. He would have to check the damage later. But for now… he’d made it through.

Voices were whispering nearby, tense and hushed. It didn’t take much effort for Gaster to overhear; he suspected they thought he was still asleep.

“...leaving you alone with him.”

“I’ll be f-fine. You know I will. He can’t d-do much right now, anyway.”

“Yeah. Maybe. I don’t know - you saw the blood, though, right?”

“It… it dusted _eventually_.”

“Only after it dried! That’s not _normal-_ ”

“Shh, Undyne, please…”

The voices, which had been rising, dropped once more.

“Well, it’s _not_. I’ve seen monsters bleed. Humans, too. And that, that was more like...”

“Y-you don’t actually think-”

“Ugh, no. ‘Course not. Just look at him. But… something’s weird, that’s all I’m saying. I mean, he should be dead, right?”

The second voice paused.

“I d-don’t know how,” they said, “but I think he only s-survived through sheer willpower. The amount of perseverance it must have taken… I- I can’t even imagine.”

“Hmph.” This seemed to somewhat placate the second voice. “Must be something pretty important. Wonder what he’s fighting for?”

As the voices slipped back out of Gaster’s attention, he wondered the same.

 

\---

 

Gaster lost track of how many times he awoke and dozed. Eventually he reached the point where he knew he was past well enough to get up, but it took a decisive effort nonetheless.

“Alright,” he breathed, his voice sounding deep and raspy to himself. Unsurprising, giving its recent disuse. He opened his eyes, taking a moment to focus on the tiled ceiling. There was a slight fuzz to everything without his glasses, and the air smelled of antiseptics and damp earth. “Alright,” he said again, bracing himself. “Now. Time To Get Up. _Come On_.”

Gaster tensed and pushed himself up to an elbow, sending small jolts of hot pain down his arm and side. His vision spun as he was reoriented, allowing him a view of his surroundings. There were a small array of machines next to his bed, softly beeping as he stirred, and a white curtain that obscured anything to his left or right. Not far beyond the foot of his bed was an unexceptional wall. A thin sheet was thrown over him, and he suspected he was naked underneath. Altogether, there was little to observe; he was certainly in an infirmary of some sort, though the doctor or nurse was nowhere to be seen.

Well, that was fine. His eclectic studies had left him somewhat familiar with human anatomy. At the very least, he was capable of diagnosing the severity of a wound. Gaster decided it would be best that the rip the bandaid off all at once, so to speak. He grabbed the edge of the cover, intending to draw it back.

And stared at the skeletal hand that clutched the blanket.

Gaster’s mind stepped through several cycles as he attempted to process what he saw.

Well, _what_ he was looking at was obvious enough: bones. He was looking at the bare bones of his hand and forearm. But what he couldn’t grasp was _how_. It was impossible, of course, for bones to operate without tendons and muscle. Unlikelier still for him to feel the coarse material of the sheets between his fingers (not to mention the absence of excruciating pain that should accompany such a wound.)

And why wasn’t it amputated? Or at least covered. Bare bones, left open to the air, capable of their own articulation - Gaster simply couldn’t grasp what he was seeing. The only logical explanation was that what he was _seeing_ was wrong. Of course. That had to be it.

Gaster closed his eyes, and took a calming breath. He counted to ten. He focused his mind inwards, evaluating his present state of mind: lucid, he determined. Calm. Focused. Gaster opened them again.

Bones. Still bones.

The monitor at his bedside began to beep more rapidly.

It didn’t make sense. It simply didn’t make any sense. He was a scientist. There was a rational explanation for everything. There _had_ to be. Just… not one he could see, at the moment. But it still existed. He merely needed to remain calm, sort through all the evidence, and figure out _what_ , exactly, _the hell was going on_ -

“Oh!” a startled voice squeaked. “Y-you’re awake! I th-thought the monitor was seeing an increase in activity…”

Gaster’s train of thought briefly flatlined as he took in the appearance of the doctor.

They appeared to be a yellow lizard. A person-sized yellow lizard, wearing a lab coat. And glasses. The sight was so unexpected and strange that Gaster had to stare for quite some time before he could confirm he was, in fact, seeing what he thought he saw. Gaster opened his mouth to say something intelligent, but stumbled over a short, barking laugh instead.

That explained it, then. Everything fit clearly into place. Gaster shook his head, chuckling as he brought a hand to his temple. The sound of bone scraping over bone reverberated in his skull.

“U-um…” the lizard doctor fidgeted under Gaster’s uncomfortably long stare. “Are you f-feeling alright?”

“On The Contrary,” Gaster said, quite sure what was going on now. “Doctor, I Believe I Am Experiencing Acute Visual Hallucinations.”

The lizard blinked. “You… what?”

“Hallucinations,” Gaster repeated. “Am I On Drugs? Or Perhaps It’s A Symptom Of A Concussion. What Is Your Diagnosis?”

“What?” the lizard repeated, seemingly flustered. “H-hallucinations? Oh, dear, I- I don’t know. You were o-on some painkillers before, but that shouldn’t cause… Maybe a concussion, but… W-what exactly are you seeing?”

“Well,” Gaster said, feeling quite sensible all things considered, “To Start, You Appear To Be An Amphibian.”

The doctor’s face wrinkled in confusion. “U-um. Reptile, actually. I... don’t understand.”

“Right,” Gaster continued. “Ridiculous, Of Course. Additionally, I Appear To Have Full Command Of My Appendages, Despite Seeming To Lack Any Kind Of Muscle Or Ligaments. Obviously…” Gaster faltered as the lizard’s response caught up with him. Wait. Reptile? “Sorry. Could You Repeat That?”

“Uh, I s-said I’m actually a reptile, not an amphibian.” The doctor wrung her hands. “I-it’s okay, though, it’s a common mistake.”

“Right.” Gaster said. He replayed her response several times in his head. Surely, he was misunderstanding what she was saying. “Right. But It Sounds Like You’re Saying You Are, In Fact, A Reptile.”

The doctor began to look worried. “U-um. I think maybe you should lay back down. I- I think you still n-need some rest.”

“Yes,” Gaster agreed. “Of Course. Excellent… Excellent Idea. This Is Not Making Any Sense…”

The lizard seemed to be relieved he’d agreed to the suggestion. “Y-you’ll need to stay here for a bit longer, I’m afraid. Your m-magic levels keep dropping. I-I’ll need to keep you hooked up to an infuser a-at least until I understand w-why it keeps happening.”

Gaster laughed as he sunk back down onto the bed. Even their brief conversation seemed to have taken a toll on his stamina, and obviously he was not well enough to be walking around on his own, no matter how rational his mind felt. “Magic Levels. Yes, Of Course.”

The lizard doctor approached his bedside as Gaster settled back in, checking several of the monitors to which he was undoubtedly connected.

“U-um. I’m Alphys, by the way,” she offered after a moment. “Doctor Alphys.”

“Gaster,” he replied. “Also a doctor. Though not of the medical variety.”

Alphys giggled nervously. “I-it’s not exactly my expertise either,” she admitted. “B-but I guess I’ve b-become a Jack-of-all-trades, recently.”

 _Sure_ , Gaster thought, in place of the more rational panic he should have felt at learning his doctor was not, in fact, a doctor. _Why not._

“Um, b-before I go,” she said, turning to Gaster. “I w-wanted to ask you a few questions. Most c-can wait until later I think. But I have to know… the way we found you… what exactly _happened_?”

What... happened.

Gaster recalled, quite suddenly, _everything_ that had happened.

“Sans!” he blurted in panic, sitting up. Hot cracks of pain ripped through his arms and chest at the abrupt movement, but he was hardly aware. Shame washed through him as he realized he’d hardly given his assistant a second thought since waking up. Alphys backed away from the bed at Gaster’s outburst. He quickly rounded on her.

“Sans! Please- Was There Anyone Else Where You Found Me- A Boy - Maybe Two If His Brother Made It- He’s Alright, Isn’t He? Please Tell Me He’s Alright.”

“I-I’m s-sorry,” Alphys stammered. “It w-was just you, there wasn’t a-anyone else-”

“How Long Have I Even Been Here?” Gaster wondered. “Where - _When_ Am I?” And to think he’d been about to just lay there, waiting to get better. He didn’t have time to waste on healing. There were so many unknowns, and Sans and Papyrus were still out there - somewhere in spacetime. Their well-being was _his_ responsibility. He couldn’t sit just sit here idly - he needed to figure out what had happened. How Sans and he had become separated. If Gaster had made it through - no matter how rough the journey - then Sans must have as well. Surely, he couldn’t be far. He was fine, probably.

Probably.

“I’m Going To Look For Them,” Gaster said, throwing the blanket aside. He paused as he took in the rest of his skeletal body, but forced himself to look away. It didn’t matter - he’d deal with it later.

“Oh, oh no, please, please don’t get up,” Alphys objected, seemingly torn between rushing to stop him and keeping her distance. “P-please you’re not well enough-”

“Well Enough To Walk,” Gaster said, sliding off the bed. His legs immediately buckled, and he caught himself on the edge of the mattress. Oof. Well, perhaps not _completely_ well…

“Oh dear, oh dear…” Alphys was taking out a cellphone and quickly dialing a number. “Undyne? Undyne, you w-were right, I need your help.”

It was just a case of mind over matter, he could do this. God, how could he have forgotten about Sans? Alphys still hadn’t said how long he’d been here, and all this time, all this time he could have been _doing_ something…

Gaster didn’t take note of the growing warmth until he’d made it towards the end of the bed, where he’d paused to catch his breath and untangle himself from the rest of the blanket. It appeared to be caught on a couple of cables, which extended between the monitors and his own body. Right, he’d forgotten about the machines. Well, he couldn’t stay hooked to them if he intended on leaving.

Gaster took hold of the tubes and traced them up to where they looped around one of his ribs (my, his mania was getting creative,) and entered his chest cavity. From there they fed into… well, Gaster wasn’t entirely sure _what_ he was looking at.

“Oh-” Alphys exclaimed, noticing what Gaster was doing. “B-be careful with that! Y-you’re still low on magic, s-so the infuser shouldn’t be removed…”

Gaster wasn’t listening. The… _organ_ , he supposed, was the source of warmth he’d been feeling. Even thinking about it made the sense grow stronger, and with it a purple haze of light.

What was it - a heart? Certainly not an anatomically correct one. It looked so delicate, like spun glass. How was it that he could he _feel_ it?

Gaster shook his head, refocusing on the task at hand. Trying to make sense of what he was seeing was futile. All that mattered now was leaving - which meant getting this thing out of him. Gaster took hold of the feedtube just beneath the point where it entered the strange, floating heart.

“W-wait!” Alphys exclaimed. “Don’t-”

Gaster yanked downwards in one swift movement.

The pain that followed wasn’t as excruciating as experiencing bodily disintegration, but it was close.

 

 

 

 

**Notes for the Chapter:**

> Gaster, don't... don't do that.


	3. Overman

**Summary for the Chapter:**

> In which Gaster begins to violently come to terms with his situation.

**Notes for the Chapter:**

> While I certainly don't expect there are many (or any) of you that are constantly refreshing the page in anticipation of the continuation of this story, I'd like to take a moment to apologize for taking so longer with this chapter. I've been on a pretty steady schedule of one chapter per week up until now, but I didn't have computer access the last week or so given I was moving across the country to start graduate school. 
> 
> On that note, I am starting graduate school, so my writing schedule will also probably be affected by that. I apologize in advanced for the likely delays. I honestly don't know what my writing schedule is going to look like, but I'll do my best.

 

 

 

Purple light filled his vision, and when it cleared he was sitting back on the bed. Gaster barely had the chance to gasp in a breath before he realized the pain had vanished, reduced to a merely jarring memory.

“What…” Gaster’s fingers curled through the gaps in his ribs as he clutched his sternum. Had he just imagined all that? It had been so visceral. What was going on?

“Oh, oh no, please, please don’t get up,” Alphys was saying. “P-please you’re not well enough to be walking around, yet.”

Gaster certainly didn’t feel well. In fact, he felt rather worn. For once choosing to heed Alphys’s pleads, he remained seated and looked down at his chest. The heart-shaped organ was still there, pulsing faintly with violet light.

“What _Is_ That?” he asked faintly.

“W-what?” Alphys followed his gaze, settling on the IV. “Oh, th-that’s for the magic infusion, like I m-mentioned before. It’s because- Oh!” Alphys’s head snapped towards one of the machine’s displays. “Oh no! I-it happened again! W-why - what’s doing this?!”

Gaster’s gaze was still on his chest, though he’d become distracted by the bones which he’d (quite pointedly) not examined before now. There were small fissures running through each of them, as if a net of crimson thread had been wound all across his skeletal frame. The cracks were filled with a very fine network of scabs, many of which now appeared to have cracked, given the blood that was seeping from them.

“I’m Bleeding,” Gaster reported flatly. His _bones_ were bleeding. Without any skin or muscles. Just... bones. "This seems anatomically improbable."

“Oh no,” Alphys continued to fret. “It m-must have something to do with your magic levels. They just dipped again. D-do you know what’s causing these sudden drops in your magic? Has th-this happened to you before?”

Gaster gave a feeble laugh. “Have I…? Has This Happened To Me Before?” He laughed again, finally letting go of his ribs. “Doctor, I Must Be Candid. I Have No Idea What’s Going On. I Don’t Know Where - Or When - I Am, Nor What I’m Seeing. I Think - I Am Beginning To Suspect There Is Something Terribly Wrong.”

Alphys looked distraught. “I, I want to help you. B-but I think I may be just as l-lost as you. Um. Can you… can you try to tell me what happened? Uh, w-without trying to run away. I- I know you said you might h-have friends out there b-but you c-can’t help anything while your magic k-keeps crashing.”

“If They’re Out There, They Need Help,” Gaster objected.

“I u-understand,” Alphys said. “I-if it’s alright, I’ll ask Undyne to go look for them. Um, she’s the one who found you. She’ll know w-where to look.”

Gaster hesitated. As much as he was impatient to be making progress, he recognized that his current approach was not the way to be doing it. He was being rash; of course he wanted to ensure that Sans and Papyrus were safe, but he honestly had no idea where to even begin looking - or the energy to try. Sending a local out to search the area made far more sense. Gaster hadn’t been acting rationally. He needed to calm down and gather the facts.

“Alright,” Gaster reluctantly agreed. “That Arrangement Is… Acceptable.”

“Oh, good,” Alphys sighed. “J-just, um, give me a moment.” The doctor stepped aside to take out her phone (hadn’t she been on it just a moment ago?) and dial a number.

She spoke in hurried tones as Gaster turned his attention back towards his anatomy. He still didn’t understand what was happening. Surely it had to be some sort of acute side-effect of the drugs - or possibly even a concussion. He couldn’t think of any other explanation. It was fascinating to watch the bones move (Gaster curled his hand into a fist) but it didn’t make any physical sense. Nothing propelled the motion. There were no muscles, no lever system of sinew and tendons. The bones simply moved, as if driven by, well, _magic_.

He would think he were dreaming if it weren’t for the pain. Even now faint, aching throbs passed through his body, especially acute in his joints and along the cracks of his bones. No, whatever he was experiencing was real - even if his mind was somehow still inhibited. Perhaps the hallucination was induced to protect him from the sight of whatever real damage his body had sustained. That didn’t explain why his doctor was was talking yellow lizard, but…

“Um, are you f-feeling any better?”

Gaster glanced up.

“Y-you just seemed to have zoned out there f-for a minute,” Alphys explained.

“Ah,” Gaster said. “I Was Just… Thinking. No Matter. Now, I Believe I Promised You Cooperation. Where Do You Want Me To Start?”

Alphys absently toyed with a tassel hanging from the edge of her phone as she thought. “W-well, if you could tell me anything about why we found you out there, a-and how you got hurt, I m-might be able to be of more help.”

“That’s Fair,” Gaster allowed. “And Those Are Two Things To Which I Actually Have Answers. However, I Must Warn You Now That It Is Likely You Won’t Believe Me. I Speak The Truth, Nevertheless. What You Do With The Information Is Up To You.” Gaster paused, expecting some protest out of his doctor, but Alphys merely gave a quick nod. “Alright,” Gaster said, “Here It Is Then. I Designed, Constructed, And Entered A Spacetime Machine. The Circumstances Of Its Activation Were Somewhat _Uncontrolled_ , However Suffice To Say That It Was Functional And Operated As Was Intended. I’ve Ended Up In An As-Of-Yet Undetermined Place And Time. The Wounds I Sustained Are The Result Of A Rather… _Turbulent_ Passage Between Dimensions.” Gaster paused once more, bracing himself for the incredulity that was bound to follow.

He certainly hadn’t been expecting Alphys to squeal in delight.

“Y-you really did it? That’s amazing!” The lizard hugged her phone to her chest as she bounced up and down in excitement. Gaster blinked, raising a bemused eyebrow. “I n-never thought that - oh - w-what’s wrong?”

“Nothing,” Gaster said, confusion turning to amusement. “I Was Just Expecting It To Take A Bit More Convincing.”

“Oh,” Alphys giggled nervously. “Well, h-honestly, it f-fills in a couple holes I had. Like, it explains h-how you got here, and, um, why you’re, um, you know, uh… d-different…” Alphys faltered and Gaster felt a pang of unease. What exactly did she mean by that? Before he could ask her to elaborate, however, (and perhaps a part of him didn’t want her to,) Alphys attempted a rambling recovery.

“U-um, you know I actually t-tried looking into spatial magic myself,” Alphys said, “b-but there’s not much literature o-on it from before the War. I tried d-design some of my own experiments, but they b-became too dangerous and I had to stop before I could learn much… But if you’ve succeeded, then m-maybe… maybe we can really get through the barrier after all!” Alphys managed to calm herself long enough to address her patient with an intent peer. “How did you _do_ it?”

“I… Well It Certainly Wasn’t _Magic_ ,” Gaster said, thrown by Alphys’s prattle. What was that about a war? And something about a barrier? “But The Process Wasn’t Terribly Complicated,” he continued, unable to resist boasting to an apparent fan. “I Merely Harnessed An Exorbitant Amount Of Energy The Exploit The Casmir Effect And Induce A Field Of Relative Negative Energy In My Lab, Temporarily Creating A Traversable Einstein-Rosen Bridge. The Most Troublesome Aspect Of The Project Was Determining Where And When In Spacetime The Bridge Was Linking To. Developing A Practical Coordinate System Was Tricky, As Of Course Our Own Reference Frame-”

“-was changing in both space and time,” Alphys finished, nodding. “Yes, I h-had trouble accounting for the relative reference frames as well… But, um, what were those names you mentioned? Casmir? Ein… Rosen, something?”

Gaster laughed, at first taking the question for a joke. “Hah! Yes, Of Course. Names Lost To The Course Of History. I Suppose Maxwell Would Be In Thrown In That Camp As Well.”

“Oh!” Alphys exclaimed, her look of confusion morphing into recognition. “Um, like the human that worked on electromagnetism? Maxwell’s equations?”

Gaster blinked. “You’re Serious.”

“S-sorry,” Alphys stammered. “I don’t know who the others are.”

“You Know James Maxwell But Not Hendrick Casmir Or Nathan Rosen?” Gaster was baffled. “Not Even _Einstein_?”

Alphys hunched beneath Gaster’s skepticism, reluctantly shaking her head.

Gaster mulled this over. The scientists she didn’t recognize were all from the 1900’s, while Maxwell was from the 1800’s. Perhaps…

“What Century Is It Here?” Gaster asked.

“Oh, um, it’s in the early 21st century,” Alphys said. Then, hesitantly, she added, “W-what about where you’re from?”

“Hm,” Gaster frowned. He absently tapped at his temple in thought, though the action was met with a strange hollow sensation that resounded through his skull. Gaster quickly stopped and tried not to think about it.

“The Same,” he responded. “But If I Didn’t Travel To A Different Time, What Explains The Discrepancy?” Perhaps he could have forgiven Alphys not knowing about Rosen or Casmir, but even the most scientifically illiterate person knew the name Einstein.

“Um, w-what about Firebrand?” Alphys asked. “Do you know Doctor Claw? Willowwisp? Newton?”

“Everyone Knows Newton,” Gaster dismissed. And what sort of a name was Doctor Claw?

“B-but what about the others?” Alphys asked. “They’re all famous scientists. A-anyone with a physics background should recognize their names.”

“They Are Not Recognizable To Me,” Gaster said.

The scientists considered each other.

“S-so,” Alphys said after a moment of silence. “Th-there’s names we both know, and names that only one of us knows. What does that mean?”

“Just… Just To Be Clear,” Gaster hesitated. He felt a little ridiculous to even have to ask. “What planet is this?”

“Earth,” Alphys said. Her eyes grew a little wider. “U-um, and what… what planet are you from?”

“Earth As Well,” Gaster said. “So. It’s The Same Planet. The Same Time Period. Yet Our Histories…”

Gaster felt his pulse quicken as the implications sunk in.

“A d-different universe?” Alphys gaped. “You’re - you’re from an entirely different dimension! That’s - oh, _wow_.”

“Wow,” Gaster flatly agreed, but it set his mind racing. “It Was Alway Possible In Theory, Of Course. We Were Cutting A Hole In The Fabric Of Spacetime Itself. But I’d Never really believed We’d Cut Into An Alternate Reality. A… A Universe Like Our Own, But Different. I… I Suppose The Machine Didn’t Work Exactly As Intended After All...”

Gaster was beginning to feel faint once more. The question was, _how_ different was this world? Was it just small ripples in the course of human history? Or were the very laws of nature changed, universal constants shifted, fundamental forces altered? He was built for a different reality - was the painful transfer from his universe to this one a result of that? And if so, had he merely experienced growing pains, or was it a symptom of a far more fatal problem.

 _Bodies reject transplanted organs._ Gaster shoved the intrusive thought away.

“U-um, Gaster,” Alphys said, drawing him out of his spiralling thoughts. “U-um, s-sorry, but, your soul’s glowing again. I- I think you should try to calm down. I k-know this is all a bit much, but you really should be more c-careful with your magic reserves so low.”

“Magic Isn’t Real,” Gaster responded automatically, looking down at the glow in his chest regardless. “Souls Aren’t Real.” The upside-down heart appeared to be suspended in mid-air, floating just behind his ribs. His ribs which he could see through. Because he was a skeleton.

The organ began to glow brighter.

“W-what?” Alphys said. “You… your world doesn’t have magic? How is that… oh no, please - magic responds to your emotions - you have to try to calm down!”

Gaster closed his eyes and breathed in. “I Am Perfectly Calm,” he said.

“Y-you, um, you don’t _look_ very calm,” Alphys said, fidgeting with her clipboard. “But you really…? What… A world without magic… What is everyone _made_ of there?”

Gaster could feel the warmth growing stronger, and with it a faint tweak in his bones. He’d felt this before, hadn’t he?

“Skin And Bones And Blood,” Gaster said. He was having trouble focussing on her words. It didn’t make sense. “Aren’t You?”

“W-well, yes,” Alphys said, “but all that’s made of magic, and i-if your world doesn’t have… oh…” Alphys edged slightly back. A strange look Gaster couldn’t place passed over Alphys’s face. “Oh. Are… are th-there even _monsters_ on your world?”

Gaster didn’t understand what she was asking. Monsters? She couldn’t be speaking literally. But then again, he appeared to be talking to a human-sized lizard. Was it possible he wasn’t actually hallucinating this? A different universe, a different reality, a different set of physical laws and evolutional paths, and… and if what he saw might actually be real, then…

The bones in his hand began to clatter as they shook, and Gaster stilled the sound by gripping the edge of his bed. “Alphys, This Is Important,” Gaster said. He could see the light glowing from inside his chest now even when he wasn’t looking at it. There was a tightness in his bones. A growing tension. He swore this had happened before.

“I Need You To Tell Me What I Look Like,” Gaster said. _Remain calm,_ he reminded himself. _Controlled. Detached._ He was a man of reason, after all.

“What d-do you mean?” Alphys asked. She was still keeping her distance from when she’d previously backed up. Something he’d said had frightened her. Gaster found that distantly and ironically amusing.

“Describe Me,” Gaster said. “Physically. What Do I Look Like.”

Alphys appeared thoroughly confused. “O-okay? I d-don’t really understand why… But if it’s what you want… Well, um, I don’t r-really know what to say. Uh, I guess for starters, y-you’re a skeleton...”

Gaster held up a hand to signal Alphys could stop. “A Skeleton,” he repeated. “Right. I’m… A Skeleton.”

He tried to hold it in his mind. He tried to accept the idea - tried to make sense of it. He had been beginning to suspect, by now, that he wasn’t suffering any brain trauma. That what he was seeing and experiencing were, in fact, real. But he’d still needed to hear it said out loud. Needed that external confirmation.

Yet he couldn’t believe it. He just couldn’t understand how… This wasn’t right. This wasn’t _possible_ . Souls, magic, and animated skeletons were so far outside his understanding of reality that he couldn’t even begin to grasp how very, terrifyingly out of his depth he really was. To believe in this reality meant that the very foundation upon which he based his knowledge and reasoning meant _nothing_.

Anticipating some sort of shock, prior to the conversation Gaster had been building walls - mental blocks - to help steady himself for whatever was to come. He’d reinforced them with reassurances of _Mind over Matter_ and that, as a scientist, his strength lay in his rationality and ability to overcome his emotions.

These walls crumbled, all at once and without any warning, as the existential horror set in.

“It’s N-Not Possible,” Gaster said, a sharp pain lancing through his chest and bones. He sucked in a breath, and he could hear the sound of his rattling bones reverberating in his empty skull. “It’s Not - How Could - Without Organs, Or A Brain, Or A Voice-Box And Lungs - It Just Doesn’t - Doesn’t Make Any Sense-” He was starting to feel lightheaded.

“Oh n-no!” Alphys exclaimed. “I sh-shouldn’t have s-said anything! I’ve j-just made everything w-worse, haven’t I? Oh no, I’m s-sorry, please, c-calm down, please, oh no…”

The heat in his chest was becoming unbearable. Gaster had felt this before, he was sure of it. Gaster clutched at his ribs, his hands illuminated by the bright purple light that was shining out, and tried to force the pain away. His breathing was edging on hyperventilation. He had to stop - had to calm down - but every time he almost managed to regain control of his breaths another surge of panic overcame him, and the building pressure only grew.

“I - Something’s Not - I Need Space,” Gaster gasped. He could feel it as if it had a will of its own. The urge to protect himself. It was like a fire within his bones, trying to manifest but ripping him apart in the process. This was wrong, all wrong. “Leave Me,” Gaster continued. “Please, I - I Don’t Know What-” Disoriented, Gaster pushed off the bed and stumbled to his feet. Alphys was saying something, but he couldn’t make her out over a roaring sound that had filled his ears. He tried to take a step but something tugged at one of his ribs, and one of the machines by his bed tipped over. Gaster stared at the broken device in a daze, before doubling over from another pulse of burning pressure.

The instinct was growing stronger, and Gaster was afraid of it. He remembered feeling something like this just after he’d arrive in this reality - and several times since. Gaster didn’t know what it was, but it was hurting him, and he _wasn’t_ going to let it happen again.

And somehow, at that thought, the sensation relented. The pressure didn’t disperse, but the incessant urge to do - do, well, _what_ Gaster wasn’t entirely sure, - snuffed out. Even so, the energy needed some other outlet. A different way to be expelled.

And Gaster wanted it out. He was barely conscious of what was happening, hardly able to grasp what each of these strange, new instincts meant, but one thing he did know was that he could rid himself of this foreign sensation simply by willing it.

So, without understanding what he was doing, Gaster forced it out. As the magic left his body it manifested into dozens of glowing, violet bones, which shot away from their origin with the momentum of their expulsion. The bones slammed into the walls of the infirmary and tore through the curtains by his bed. They left craters where they impacted, carving deep gouges into the tiled room’s ceiling and floor.

Gaster was immediately left feeling weak, and he sunk to the floor where he stood. The roaring in his ears subsided. Somehow, the drained feeling didn’t make him feel any better.

“...Oh… oh d-dear...”

Groggily, Gaster looked up. His vision blurred in and out of focus. Alphys was standing off to the side, holding something to her waist. Something small. It was… a bone.

Blood dripped to the floor, coiling away in a wisp of dust. It took Gaster far too long to realize where it had come from.

“...Oh no…” Alphys said, clutching the bone that was lodged in her gut.

Alphys collapsed to the floor a moment later. The bone dissolved into shreds of light as its head smacked against the ground, and left open the wound it had carved in her abdomen. Blood poured out in a thick, steady wave. Before it could pool very far, however, the edges dissolved into a powdery white dust, equal amounts of which blew away, and blew back into the red puddle from which they had emerged.

Shock and this sight were the last things to pass through Gaster’s mind before he blacked out.

 

 

 

**Notes for the Chapter:**

> Whoops.
> 
> Gaster is basically what happens when you hand a kid a gun. He's really not trying to hurt anyone, but he has no idea how to wield this new power. At this point its operating largely on instincts and emotions. Every time he feels threatened or anxious, his time-travel abilities try to pull him out of the situation. (It doesn't help that the strain of the time jumps is only re-damaging his already fractured body.) When he actively fights the jumps, they respond, but all that magic has to go somewhere.


	4. Eternal Return

**Summary for the Chapter:**

> Survival of the fittest dictates that one must either adapt to new environments, or perish. With little else to turn to, Gaster embraces adaptation, though he is beginning to discover the environment in which he has been cast is more hostile to his nature than initially judged.

“R-really, Undyne, this isn’t necessary.”

“Like Hell,” Undyne snarled. “I knew I shouldn’t have left you alone with him.”

“N-nothing happened,” Alphys insisted. “Really, I sh-shouldn’t have said anything. It was just… just a feeling, is all. He- He probably isn’t even c-conscious right now.”

Undyne crossed her arms across her chest, glaring down at Alphys as she harrumphed. “And why do you think that?”

“W-well,” Alphys said, flinching under Undyne’s intense gaze. “You know, like I s-said before.... H-his magic crashed again. He w-was getting really upset a-and was trying to get up w-when there was this… this… um, I guess, _impression_ that he was about to do magic, b-but!” Alphys hurried added as Undyne’s face soured. “-But then he just passed out and his magic levels a-almost dropped to zero. I’ve given him another magic transfusion since, b-but I still think he’ll probably be out for a while. S-so that’s why,” Alphys swallowed, “that’s why this _r-really_ isn’t necessary…”

Undyne stared at Alphys for several quiet, unnerving seconds. Then she sighed, and dropped her arms to her side. “You’re probably right. It probably _isn’t_ necessary.” Alphys momentarily sagged in relief, mostly grateful Undyne hadn’t bothered to ask what, exactly, had caused her patient to have a panic attack in the first place. Undyne wasn’t done, however. “But I don’t care if that’s true, because this is about what _I_ want. And I want to go check on him.” With that, she sidestepped Alphys and made for the infirmary.

“Ah! W-wait!” Alphys cried, hurrying after the Captain. “You’re going to wake him!”

Undyne ignored the shouts of caution, throwing open the infirmary door and crossing to the single occupied bed in three quick steps. She shoved back the curtain, revealing a very startled skeleton.

“Good Lord!” he cried, pulling the bedsheet up his chest as if to cover his modesty. Apart from his bones and soul (glowing, briefly, from the surprise,) there was little to hide; even so, Alphys realized it was probably past time she found some clothes for him to wear.

“Looks like he’s awake,” Undyne observed. Alphys shuffled over behind her.

“What On Earth Are You Supposed To Be?” Gaster wondered aloud.

Undyne’s ear fins flared indignantly. “The Hell do you mean by that?” she demanded. Before he could be allowed to clarify, however, she provided an answer herself. “I’m Captain of the Royal Guard. Which makes you my prisoner until I decide what to do with you.”

“Prisoner?” Gaster seemed surprised. At a flicker of movement from behind Undyne, his attention was quickly drawn elsewhere. “Oh, Thank God,” he said, the tension going out of him as he caught sight of Alphys. “You’re Alright.”

“She’s alright?” Undyne repeated, her eyes narrowing. “What exactly do you mean by _that_?”

“Er,” Gaster hesitated, grimacing. “That Would Be Difficult To Explain.”

“Try me,” Undyne said, advancing a step closer.

One of the monitors at Gaster’s bedside beeped, and Alphys hurried over to check on the readouts. His magic levels were recovering, which was good, but his health remained low, likely related to the fissures that covered his body. She still needed to ask him about that. She thought she recalled him saying his injuries had something to do with his extra-dimensional travel, but… something didn’t feel right. Alphys felt like she was missing something. A lot of things, probably. They needed to talk.

And for that, she needed him all in one piece.

“Undyne,” Alphys said as she changed out the nearly-empty bag of magic infusion. “I d-don’t think intimidating him is g-going to help anything.”

Gaster raised a brow. “Am I Supposed To Be Intimidated?”

Undyne growled. “I don’t trust you,” she said. “And I _really_ don’t like you.”

“I Assure You The Feeling Is Mutual,” Gaster said, partially rolling his eyes. Undyne was nearly steaming. “Doctor,” he said, turning his attention back to Alphys, obviously having decided she was the only one worth talking to, “In Light Of Recent _Discoveries_ , I Was Hoping We Could Have A Private Conversation-”

“Look here, you punk,” Undyne interrupted, her eye flashing. “I wasn’t _finished_ , and I’m not gunna be done with you until I’ve got some answers.”

Gaster’s skeptical look shifted from Undyne to Alphys. “Is She Always Like This?”

Something in Undyne snapped. “Alright, smart guy.” A flash of green light surrounded Gaster, which appeared to perplex him more than anything. It wasn’t until he attempted to move—and couldn’t—that the purpose of the magic became clear. “Now that I have your attention, there’s some things I want to-”

A small army of purple bones materialized in the air about the room before Undyne could finish her thought, honing in on the Captain.

“Oh, Damn, Not Again,” Gaster sighed, at the same time Undyne said, “What the Hell?!”

“Th-that’s new,” Alphys noted, edging away from the nearest construct. She found herself somewhere between fear and fascination. Would he really hurt them? She didn’t know this man at all, but something in her wanted to trust him. Maybe it was simply their shared scientific background—or perhaps it was just her innate curiosity that blinded her. For someone who claimed to be from a dimension with no magic, Gaster appeared to be wielding it quite well—and quite a lot of it, too. Even this sudden display rivalled what Undyne was capable of. Which, Alphys belatedly realize, probably wasn’t a good thing, given present company.

With a blaze of green light, a spear appeared in Undyne’s hand, and an array of the weapons formed behind her. The spears spread out, taking a defensive stance against the sharpened bones pointing their way. Undyne leveled her weapon towards Gaster’s chest, her eye narrowing.

“You wanna _go_?” she challenged. The room crackled with magic, emerald and violet hues casting strange shadows around the medical bay.

Any other monster, caught on the wrong end of Undyne’s spear, would have been quaking in their boots and (if able) beaten a hasty retreat. Gaster, however, merely appeared to be burdened with a sudden and strained concentration.

“Go?” he asked, clearly distracted. “Go Where?”

There was a moment of silence. Each occupant of the room appeared to be processing a different part of this exchange. Bewildered, Undyne turned to Alphys.

“Is this guy serious?”

Honestly, Alphys didn’t know.

“Sorry,” Gaster said, appearing to be apologizing more to Alphys than Undyne. “This Isn’t Intentional. I’m Trying… Trying Not To… I Can’t Explain-”

Alphys finally put it all together. “Oh! Undyne, l-let him go!”

“What?” She gestured her spear wildly around the room. “He tried to attack us!”

“I-it’s self defense,” Alphys said. “He c-can’t control his magic. It’s just responding instinctively.” Did that have something to do with his crashes? Every time she’d witnessed his magic drop he’d been getting worked up about something beforehand. But where did that missing magic _go_?

“ _He can’t control it_?” Undyne repeated. “Why the Hell can’t he control his magic?” Undyne rounded on Gaster. “Why the Hell can’t you control your magic?”

“Er.” Gaster’s concentration still appeared elsewhere. Beads of magic had broken out over his skull. “First, Could You Not…?”

Undyne made a displeased noise, and looked to Alphys. Timidly, the doctor nodded her head, and Undyne let out a disappointed sigh. With a gesture she banished her horde of spears and, after a moment reluctance, the green magic that kept Gaster pinned in place. The skeleton sagged in relief, his bone constructs vanishing almost at once. Alphys also relaxed; that was one crisis avoided, at least. Now to navigate through the rest of this minefield-of-a-conversation.

“Let’s Not Do That Again, Shall We?” Gaster said.

“You didn’t answer my question,” Undyne said. “Why can’t you control your magic?”

Gaster hesitated, shooting a glance towards Alphys so quick she nearly thought she imagined it. She could tell a plan was formulating in that mind of his, but she couldn’t tell what.

“Amnesia,” Gaster said. “I Don’t Remember Anything. Must Have Been An Accident.”

“Amnesia,” Undyne repeated, the skepticism clear in her tone. She turned to Alphys. “Can Amnesia cause you to forget how to use your magic?”

“U-uh-um,” Alphys stammered at being put on the spot. “In s-severe cases, um, I suppose it’s _technically_ possible—that is, I mean—um, yes, i-it could happen. One could… could forget how to wield their magic…” Alphys was shaking. She wasn’t lying, directly, but she knew for a fact Gaster wasn’t suffering from amnesia. Undyne probably deserved to know that, too, but if she called Gaster out on his falsehood now… Well, she suspected civil conversations would become a thing of the past. With no small amount of effort, Alphys met Undyne’s gaze, and tried to still her shaking.

Alphys was intentionally misleading Undyne.

She felt like trash.

Satisfied with the explanation, though not entirely pleased by it, Undyne turned her attention back to Gaster. “You can’t remember anything?” she pressed. “Where you came from?”

“Nothing,” Gaster responded immediately. Then he faltered. “Actually… There Is One Thing. Two Companions Of Mine. You Haven’t Found Them, Have You? I Must Know If They’re Alright.”

“Oh, yeah,” Undyne said, tipping her head back towards Alphys. “Alphys mentioned that. I went looking, after I brought you in, but there wasn’t anyone else in the area. Echo flowers didn’t pick up any other voices, either. You sure you were with others?”

“I… I’m Not Sure, Actually,” Gaster admitted. “I Thought They’d Be With Me, But…” he trailed off, lost in thought.

“Anything else you can tell me?” Undyne asked. “If there is anyone else out there that’s got answers, I’d like to know. What do your companions look like? They also skeletons?”

“No,” Gaster said. “Well… Actually… I Don’t Think So But- But I’m Not Sure…” Something of the genuine concern and doubt in Gaster’s voice must have rang true, for Undyne backed off. It wouldn’t have been obvious to anyone other than Alphys, but she couldn’t miss the subtle shift in Undyne’s stance, and the slight softening of her frown.

“Alright,” Undyne relented, stepping away from the bedside. “It’s fine. If you remember anything, let me know. In the meantime, I’ll have the dogs do a sweep of Waterfall. See if we can turn anything up. Alphys?” she asked, turning to the doctor. “You sure?”

She was referencing a rather tense conversation the two had held before Undyne had burst into the infirmary. Undyne didn’t like Alphys being alone with the stranger—and she suspected that was especially true now that she’d seen his magic potential. But the fact that she was asking meant she trusted Alphys’s judgement, and was at least willing to compromise. Alphys might have blushed if she weren’t so incredibly stressed.

“Y-yeah,” Alphys said with less conviction than she would have liked. “Yes. I’m sure. Th-thanks, Undyne. I- I’ve got it from here.”

Gaster observed this exchange with apparent curiosity, but didn’t comment. Hesitating only a moment longer, Undyne turned to go. “Right. I’ll be back to check on things later.” Without any further formalities, the Captain left.

Both scientists seemed somewhat relieved with her departure.

“Th-that was dangerous, you know,” Alphys said once she was sure Undyne was out of earshot. “Why did you lie to her? It w-would have been bad if you’d been caught.”

“I Suppose It’s A Good Thing I Wasn’t Caught, Then,” Gaster said. He gave a dismissive shrug. “It Seemed The Best Way To End Her Line Of Questioning, And Also Served To Explain My Unfamiliarity With, Well, _Everything_ Around Here. Besides,” he added, “She Didn’t Strike Me As The Type To Delve Into Theories On Multiverses And The Subtleties Of Spacetime Manipulation.”

Alphys had to agree with him there. She hadn’t yet told Undyne where Gaster claimed to be from for precisely that reason. Well, that and the fact that she still had questions of her own for the doctor.

“S-still,” Alphys said. “D-don’t do something like that again. She might not have believed you.”

“She Did, Thanks To You,” Gaster pointed out. “Why Did You Help Me, Anyway?”

“B-because…” Alphys hesitated. It might be selfish, but it was the truth. “Because I want to learn more about y-you—and your world,” Alphys said. “A-and also, if everything you’ve said is really true, th-then you might be our best bet at getting to the Surface. If I’d c-contradicted you in front of Undyne… well, things w-would probably be a lot worse for you right now.”

Rather than be moved by the implications of Alphys latest words, Gaster merely smiled. “How Rational,” he said. “I Like The Way You Think. And What You Request of Me Is Also That Which I Request Of You, If You’d Allow It. There Is…” he faltered, looking down at one of his hands as flexed his fingers. “...Quite A Lot I Wish To Learn About This Place.”

“I’m sure we b-both have too many questions for our own good.” Alphys smiled weakly. “I d-don’t even know where to start.”

“I Do,” Gaster said. “I Want To Know About Magic.”

Alphys tipped her head. She’d expected something more specific. “Th-that’s a broad subject. W-what do you want to know about magic?”

“ _Everything_ About Magic,” Gaster said. “Teach Me Everything.”

 

\---

 

Alphys couldn’t teach him everything about magic, but she explained to him as much as she could. Gaster listened intently, only interrupting to ask for clarification—if he’d had a notepad and pen, she had no doubt he’d be taking notes.

_“Soul; essence of your being. Treat well.”_

The conversation had naturally developed into the differences between monsters and humans and, from there, to the War that had left them trapped in the Underground. This seemed to particularly trouble Gaster. On more than one occasion he began to ask a question before stopping himself, reconsidering his words, and bidding that Alphys continue. She wasn’t sure what it meant, except that it likely had to do with the differences between his world and hers. It wasn’t until after she’d spoken of the Barrier — and the only known ways to pass through it — that Gaster appeared to be in more familiar territory.

“And That Is Why You Think I Can Help,” he said, tapping his finger in thought. “Perhaps My Spacetime Research Could Provide Some Way To Bypass The Barrier.”

“Th-that’s my hope,” Alphys said.

“You Do Realize,” Gaster said, “That My Very Presence Here Means My Project Was A Failure? Or At Least, That It Did Not Operate As Planned.”

“Y-yes, I thought of that,” Alphys admitted. “But, but if you could do a-all that with just basic technology, th-then I _know_ it can be done with magic! I just know it.”

“Hm,” Gaster considered, smiling lightly at her enthusiasm. “Perhaps You’re Right. It’s Possible I Was Working Without A Complete Set Of Instructions. I’d Be Lying If I Didn’t Admit I’m Interested In The Prospect… And Of Course, It Aligns With My Own Self Interests. I Must Attempt To Get Home—And Ensure The Wellbeing Of My Colleagues.”

“Uh, um, about that,” Alphys said. She felt awkward bringing it up, but since he hadn’t yet offered the information she saw little other choice. “Your world. You s-still haven’t said much about it.”

“Ah, Right,” Gaster said. “Apologies, Doctor, A Deal Is A Deal. What Is There To Say About My World?” he mused, pausing for a moment to collect his thoughts. “Certainly You Know, As I’ve Said, That Our Reality Lacks Magic, Which Means That We Lack Souls As Well. At Least, We Lack Any Physically Detectable Ones, Though Both Souls And Magic Remain Prevalent In Religious And Mythological Texts Throughout Our History. Perhaps, Then, There Might Have Been More Truth To Those Stories Than I Gave Them Credit… Regardless,” Gaster said, steering himself back on track. Alphys was already beginning to get the impression that the skeleton was prone to long and rambling digressions. “Because We Have No Magic, Everyone Takes An Entirely Physical Form, And Because We Have No Souls, The Tensions That Led To Your War—And Being Sentenced To The Underground—Never Transpired On Our Earth. However, We Yet Managed To Find Ways To Fight Amongst Ourselves. Two World Wars, In Fact, Driven By Political and Ideological Differences, Though I Supposed That Is Neither Here Nor There. Our Technological and Mathematical Developments Seem To Largely Parallel Each Other, At Least From What I’ve Gathered So Far. Spacetime Manipulation Was Still In The Realm Of Theoretical Physics, Until I Put It To The Test. And Perhaps With My Departure It Will Continue To Be Regarded As Theoretical For A While Longer.”

“No Underground,” Alphys mumbled to herself wistfully. “That… that would be nice.” Something else was troubling her, however. “You said that everyone there is physical… even monsters?”

“Everyone,” Gaster simply repeated. Alphys waited for expanded clarification, but it didn’t come.

Maybe she was overthinking it, but… she just couldn’t understand how monsters could exist without magic. That kind of universe was terrifyingly foreign to her. And still, Gaster hadn’t explicitly _said…_

“S-so,” Alphys hesitated, the question making her shake. “You… you said before you weren’t, um, weren’t a skeleton… in your world.”

Gaster met her gaze levelly. “That Is Correct.” Again, he didn’t elaborate.

Alphys swallowed. “Um… then what… what did you look like?”

Gaster shrugged casually. “Significantly More Fleshy, If That’s What You Mean. Organs, Muscles, Cartilage, Skin. You Know, I Have A Theory On That. Perhaps The Mass That I Lost Was Needed In Order To Create A Soul. A Conversion From Matter To Energy, As It Were. I Suppose I Should Be Grateful It Did Not Take All Of Me…”

Alphys was losing his attention; he’d quickly be on to another subject if she didn’t intervene. She almost let him, too. But there were still too many warnings she just couldn’t let go. The way he’d reacted to her and Undyne’s appearances, for instance.

“A-and,” Alphys said, forcing herself to interject. She’d broken out in a cold sweat, but couldn’t let herself stop now. “A-and. And you, um. On y-your world. You. W-were you a m-monster or…?”

Gaster’s face was impassive. “A Monster, Of Course. Why Do You Ask?”

“Oh,” Alphys said, quickly looking away as she busied herself with checking the bedside monitors. “Of course, it w-was a silly question, um. N-nevermind. Uh, um, did you m-mention wanting to learn more a-about our history earlier? I m-may have some books I can bring by. They sh-should be able to help.”

“That Would Be Greatly Appreciated,” Gaster said, either unaware of Alphys’s agitation and rash change of subject, or choosing to ignore it. “Anything On Maths Or Magic As Well.”

“W-we don’t have a lot of technical books i-in the Underground,” Alphys admitted. “But I have a small collection. I’ll bring some next time I check on you.”

“Thank You, Doctor,” Gaster said. He sounded sincere.

Alphys didn’t really remember the rest of the mumbled pardon she’d stammered out, or how she’d gotten from Gaster’s bedside to the room outside the infirmary, but once the door closed behind her she sagged against it, and took several calming breaths. She could feel her soul fluttering nervously in her chest.

She didn’t know if he was lying. She really didn’t. But if not lies, then he certainly wasn’t telling her the whole truth. Maybe her growing unease would have been alleviated with the last conversation they’d held, had she not processed what the displays had read.

Magic: 500/500

The machine was designed to encompass the magical potential of 90% of monsters, which of course meant a small population maxed out the readings of the device. This was surprising to see with Gaster, especially after all his magic crashes and large number of summoned constructs, but not intrinsically worrying. No, the truly concerning moment had come when she’d thought to remove the magic infuser only to find that it was nearly empty and _still being drained_. A typical soul would simply stop accepting magic once its reservoir was filled, however Gaster still appeared to be recovering. Alphys had no idea how much magic a soul like that could hold, but based on the infusion levels… it was at least double that of an average monster. Probably more.

She’d seen readings like this before. Both with King Asgore… and with the human souls.

Alphys still hadn’t decided what this meant, but she was sure of one thing. There was something more to Gaster, and she was going to figure it out.

 

 


	5. Tralfamadore

**Summary for the Chapter:**

> In which Gaster meets an old acquaintance.

**Notes for the Chapter:**

> Time Differential: An infinitesimally small change in time so brief that it is, in effect, instantaneous.

 

 

 

“R-ready?”

Gaster braced himself. “Yes, Of Course. At Your Leisure, Doctor.”

Alphys nodded; Gaster couldn’t help but notice how she looked more nervous about the procedure than him. There was the faintest prick of discomfort—and then Gaster gasped as the phantom pain of a moment much like this came back to him all at once.

 

\---

 

Gaster decided he was dreaming. He was conscious, but his surroundings were an empty void. It wasn’t black, exactly, so much as an absence of light—absence of sound and sensation as well. When he tried to move, his efforts were only met with the impression that it had taken place.

“Stay Close.”

The voice was mute and wrung with static. Echoes preceded it and the sound was barely audible, but the words’ meaning cut through the abyss more clearly than any physical noise could. In fact they were hardly words at all; Gaster could feel their intent in his very bones.

Somehow, it was familiar.

“Causality Would Not Enjoy Us Slipping Into A Parallel Dimension At This Differential.” A laugh bubbled through the darkness like boiling tar. “Though Perhaps The Ensuing Chaos Would Be Fun.” The speech reached Gaster in a cacophony of overlaid tenses. _Would be, has been, was, will be_ … He had to struggle to pay attention to the larger message when falling into the reflection of other meanings was a perilously easy feat.

The laughter, he thought, did not sound entirely sane.

 _“What Is This?”_ Gaster asked, or tried to. His voice made no sound, but the Other seemed to have understood regardless.

“Nothingness,” it said. “The Singularity Between Past And Future. Ah, Here.” A blackness swirled against the dark, coalescing into a vague shape that might, at one time, have been a person. Their silhouette never quite stabilized, and their inky form periodically slid in and out of focus. Gaster found himself unable to look long at the being—his gaze unwillingly slipped away with the slightest lax of focus—but he could make out something cracked and dimly glowing in its chest.  

“You Learn To Give Form To The Void Eventually,” it said. _I learned, you will learn, we are learning_ … “Though For No Other Reason Than That We Could. We Underestimated The Tedium Of Timelessness.” It laughed again. “You Will See, I Suppose…”

Gaster was beginning to feel unwell. He thought his chest ached, though he couldn’t even be sure, in this place, if he even had a chest or body at all.

“Ah, That Is Because This Is Not A Place For Creatures Of Continuity,” the voice said, as if reading his thoughts. “The Soul Is Strained Outside Of Spacetime. It Wants To Snap Back. But Do Not Fear, You Will Not Be Damaged By This. At Least, Not At This Differential. We Are A Special Case, After All.”

Gaster wasn’t following much of what the spectre was saying. The discomfort was growing, and his mind was overcome with strange thoughts. Memories, perhaps. An impression of recognition washed over him.

“ _I’ve… I’ve Been Here Before?_ ” he thought.

“Oh Yes,” the Other said. “Several Times Now, And Many More To Come. You Are Unstable,” it added. _I was, I am, you were, you will be…_ “What Is The Last Thing You Remember?” The being regarded Gaster, and he could feel some of its will pass through him. It felt indifference, jealousy, pity, amusement, disappointment, weariness.

“ _Alphys_ ,” Gaster struggled to remember, partly in an effort to distract himself from the Other’s unnerving presence. “ _I… She Was Going To Remove My IV. And Then..._ ” He couldn’t remember what had happened after that.

“Then You Came Here,” the Other said. “Another Time Jump. Your Powers Activate At The Slightest Threat To Your Nerves.” It sounded unimpressed. “They Would Settle Down In Time, But That Is Not How Events Transpire. I Will Fix It At This Differential.”

“ _Fix_?” Gaster repeated.

Something numb wrapped around Gaster’s core. The sensation spread through Gaster’s body in a surge of white noise, prickling with nonexistence. Gaster instinctively attempted to pull away from the hold—and very nearly succeeded. Unamused, the grip strengthened.

“Enough Of That,” the Other said, “I’m Helping You. Be Grateful It Is Me—And Not A Later Version Of Us—That Experiences This Interaction. Such Unending Existence In The Void Leaves Our Eventual Self Quite _Unhinged_.”

A pressure was being drained from Gaster. It didn’t leave him feeling weakened, but the sensation unnerved him nonetheless. It felt wrong on an intrinsic level, and caused him to lose focus on what the Other had said. (He’d felt, for a moment, as if some understanding of the Other’s cryptic language and been about to crystallize. Things were happening too quickly, however, for him to fully process.) Helpless to resist, Gaster watched as the energy flowed out of him and the dim light in the Other’s chest began to glow. The being let out a sigh of relief, and for a moment a strange weariness rippled from it. Then the impression abruptly cut off, as if the Other realized it had let slip some of its sentiment, and a change began to take shape.

Form appeared from the formless. Light and color slowly percolated from the void, resolving into a wall of indistinctly moving shapes. It took some time for Gaster’s sight to adjust and give name to the creation. It appeared to be a window back into reality—or at least out of whatever dimension he was currently in.

 _“What Are You Doing?”_ Gaster asked.

“Harnessing The Overflow,” The Other said. “You Are Operating With An Excessive Amount Of Magic. Normally I Am Merely Capable Of Observing The Continuum, However With Your Surplus Magic—And Presence—I Am Allotted More Tangible Interactions.”

The colors in the window resolved into distinct features. Red and orange hues dominated the screen, and steam wavered up through grated walkways. Metal pipes wormed in and out of volcanic rock, and Gaster could see hints of a larger facility embedded in the landscape. The current scene, however, was too close-up to make out much of the surroundings. It was centered on two figures, in fact, the first of which was tall, wearing a dark lab coat, and a skeleton.

Perhaps it could be forgiven, given the recent circumstances of his appearance, but it took Gaster far longer than he would have cared to admit to recognize the figure.

_“Is That… Me?”_

“It Is,” said the Other. _It was, it has been, it will be..._

Gaster watched as his doppelganger sprinted down a smoking hallway.

 _“What Is He—What Am I Doing?”_ Gaster asked. _“I Don’t Remember This.”_

“Not Yet,” the Other agreed.

Gaster’s gaze shifted to the other figure: also a skeleton, but smaller. _“And Who Is That?”_

“So Many Questions,” the Other chuckled. “As For Your First…”

On the screen, the two skeletons abruptly vanished with a faint pulse of blue. The scene shifted to a different location, and the skeletons reappeared. Immediately the two summoned a wall of glowing bones, which linked together to shield the floor from falling debris. It took Gaster a moment to realize there were others in the room as well; once the debris was taken care of, Gaster (the one on the screen) and the other skeleton moved to help the bystanders. Then, one by one, the smaller skeleton took hold of individuals, vanished, and returned alone. Finally, Gaster was able to find something in all this madness that was beginning to make sense.

_“We’re—They’re Rescuing Them?”_

“Yes,” the Other said. “The Core Was Deteriorating, About To Be Consumed By The Magma. We Tried To Save Everyone.” This time, the specific use of pronouns did not escape Gaster’s notice. He looked again at the Other, trying hard to see through the miasma that threatened to obscure its identity.

 _“I… I Know You,”_ Gaster said, recognition slipping away even as it formed. It was as if his mind were wading through syrup. A frustrating resistance met each thought.

“Oh Yes,” the Other laughed. “Intimately. Though Perhaps It Might Be Said That I Know You Better Than You Know Me. Look,” it added, and the nearly pinpointed identity crumbled from Gaster’s mind as his attention was drawn back to the window. The figures were still running, fighting, and fleeing. Gaster didn’t know what he was supposed to be looking for.

“We Tried To Save Everyone,” the Other repeated. “We Thought We Were Thorough. But, Then Again, We Ran Out Of Time…” Gaster sensed a wave of self-aware irony accompanying this last statement, though the meaning of such a sentiment was lost on him.

Through the window, the two skeletons rushed through a room; an array of purple, floating hands righted an overturned table, and a glow of blue embraced and raised a segment of fallen ceiling. Once done with their search the skeletons moved on; the scene, however, did not shift to follow their progress. After a moment it instead drifted towards a locked supply closet in the back of the room, whereupon the window magnified to display its contents. The room was partially collapse, and a ventilation shaft jutting down from the ceiling had crushed a supply shelf. All manner of supplies had been spilling onto the floor, which partially covered a figure that lay unconscious among the mess.

“Unfortunately,” the Other said, “Despite Our Best Efforts, We Were Unable To Find Everyone.”   

The facility rumbled, but the unconscious figure did not stir. Gaster felt uneasy.

 _“They’re Going To Die Here?”_ he asked, already suspecting the answer.

“If Nothing Intervenes,” the Other said, “Yes, They Die.”

 _“Please,”_ Gaster said. _“I Don’t Want To Watch That.”_

“You Will Not Have To,” the Other said. “That Is Why I’ve Stopped You Here.”

The static around his chest tightened, and Gaster felt something begin to pull at his essence once more. The light inside the Other grew brighter, and its form grew stronger and more distinct.

“My Soul Is Shattered,” the Other said. _Was shattered, will be shattered, has been shattered..._ “And My Magic Virtually Nonexistent. I Would Not Be Able To Sustain Myself For Long Back In A Physical Realm. You, However, Provide More Than Enough Magic To Allow For Interactions.”

The Other reached out, and disembodied hands pressed against the window. There was resistance, and Gaster flinched as he, somehow, felt a similar pressure overcome him. With a surge of magic, the window rippled and the hands pressed through.

 _Bones_ , Gaster recognized, now that they weren’t obscured by the void. Bone hands. Like he’d seen a few moments before—the magic his counterpart on the screen had been using.

Carefully, they extracted the unconscious monster from the debris. The form stirred as it was lifted, groaning from apparent injuries that flaked with dust. Just as it was raised to the window its eyes flickered open, and it lifted its head.

Gaster couldn’t say, exactly, what the window might have looked like from the outside, but the reaction of the injured monster gave him some indication. Drowsy confusion turned quickly into a look of horror, and the monster let out a yelp just as it was pulled into the void.

Gaster once more felt resistance in his magic as the barrier was crossed. The monster’s cry was cut off as it entered the void, and Gaster was no longer able to make out its form. He could still see its soul, however, which burned like a torch in the darkness. It wasn’t until then, when he had a benchmark to compare against, that he realized how dim and broken the Other’s soul was. Even bolstered by Gaster’s magic, it remained faintly flickering. For a moment, the sight made him feel sad.

Panic cut through the emptiness. The Other hummed, displeased, but otherwise ignored the frightened soul. The window began flicking between scenes elsewhere in the science facility as the Other resumed their search, leaving Gaster to cringe away from the buffeting swells of horror that radiated from the new soul.

 _“What Are You Going To Do With Them?”_ Gaster asked, unable to endure it for long.

“Transplant Them To A Different Spacetime,” the Other said. “One Of A Less Hazardous Environment, Ideally.” The window landed on a scene of another two monsters, these trapped in a secluded office whose door was alight. The hallway outside the room was also on fire, and smoke was leaking in under the door. Drowned out by the roar of the flames, the monsters’ call for help went unanswered.

The Other summoned several more sets of hands, and sent them out of the void. The trapped monsters didn’t see or hear the descending hands, themselves facing the other way, but let out a startled yelp as they were seized and lifted into the air. Once more Gaster felt a strain on his magic as they were reeled in, and quickly felt their confusion turn to desperation and panic as they were swallowed by the abyss. The two new souls joined the other, and the three huddled close together, as if taking comfort from the only familiar aspect in this strange, new environment.

Gaster was worried about them, and his concern was in no way assuaged by the abstract shudders of fear that continued to emanate from the monsters.

 _“Are They Alright?”_ Gaster asked, wishing there were more he could do than simply watch.

The Other gave off the impression of thoughtfulness. “At This Differential, I Am Not Sure How Exposure To The Void Will Impact Their Health,” it admitted. “Souls Are Not Meant To Persist In The Void. Still, I Believe The Risk To Be A Better Option Than Their Alternative Fate.” This did little to comfort Gaster, though he found himself in reluctant agreement. Leaving them to perish in the fire would have been unthinkable.

“However,” the Other continued as it navigate to yet another scene. “At A Later Differential, I Will Discover That Their Transplantation Resulted In Unintentional Side Effects. They Become… Somewhat Unstuck From Spacetime, Like Myself. Not To The Same Extent, As They Still Largely Persist On The Physical Plane, Yet There Are Similarities…” The Other shook its head. “I Will Find It Peculiar, As Sans Is—”

 _“Sans?!”_ Gaster interrupted. _“Is He Alright? Where Is He?”_

“—Capable Of Transplanting People Through Spacetime Without Any Adverse Effects,” the Other continued, ignoring Gaster’s outburst. “Perhaps It Is Simply That My Magic Was Never Intended To Be Perverted In Such A Way. I Will Always Wonder About This.”

A fourth, unconscious monsters was pulled into the void. Gaster only caught a glimpse of the last one; it was small, the size of a child. His thoughts, however, were still spinning with the Other’s words. It knew something of Sans. He could… transplant people? The other monsters would become unstuck from spacetime? It was too much to process. One thing at a time.

 _“How Do You Know What Will Happen To Them?”_ Gaster asked.

There was laughter.

“I Forget What That Feels Like,” the Other remarked. “Not Remembering What Will Be. Oh, That Mystery Would Be Fun To Experience Again. Maybe At The End, Maybe…”

The window changed, this time displaying a gentler environment. The angry reds and oranges had subsided into more muted hues, and the roads were empty and quiet. The monsters souls, Gaster noticed, had grown quiet as well. It began to seem as if he and the Other were alone in the void once more.

“The Seems Suitable,” the Other said to itself. Unceremoniously, it gathered up the souls and moved them towards the window. “Do You Remember Reading That Vonnegut Book As A Child?”

It took Gaster a moment to realize the Other was addressing him. _“Oh, Ah, No, Not Particularly,”_ he said, caught off guard by the non sequitur.

“Perhaps You Should Reread It,” the Other said. “There Is A Recurring Species In His Novels—Tralfamadorians. They Are Four-Dimensional Beings, And So Exist Outside Of Time. This Makes Them Capable Of Experiencing Their Past, Present, And Future Simultaneously.” The Other paused, considering. “Perhaps Its Premise Is Not Entirely Accurate, But It Communicates The Principal Well. Reread It,” the Other said again. “It Will Help You Understand What Is Happening When… Well. I Suppose That’s Still A Long Ways Off From Your Reference Frame.” The Other deposited the souls back into reality, where the monsters’ bodies reformed. Gaster couldn’t be sure, but he thought the monsters looked more dull than they had before. Had they always been shades of grey?

The Other looked through the window, waiting until the monsters began to stir. After a time it appeared satisfied, and the window blinked out.

Gaster felt the full attention of the Other turn on him once more. This time Gaster couldn’t feel anything from the Other as it kept its impressions carefully in check. Somehow, Gaster found this more unnerving than being able to sense its unstable thoughts.

 _“What Now?”_ Gaster asked, dreading the answer.

“Now…” The Other shifted. Then, slowly, the static pressure in Gaster’s chest withdrew. “Now, You Snap Back. You’ve Served Your Purpose Here.”

Gaster was flooded with relief. The presence of the Other was unnerving on multiple levels, and he had no desire to continue to be used by it like a disposable battery.

Yet the scientist in him couldn’t help but be itched by the fact that this stranger seemed to know so much about everything—about things Gaster could hardly comprehend.

 _“Wait,”_ he found himself saying, even as he felt himself begin to drift away. _“Before I Go, I Have Questions.”_

The Other watched him. “Ask, And I’ll Answer,” it said. “For As Long As You Can Stay Here Without My Help. However It Is Only Fair To Warn That You Won’t Remember Interactions With Myself Once You Leave.”

Gaster pushed back against the void, trying to ground himself. There was nothing, of course, to push against, but Gaster was beginning to intuit how to navigate some of the more abstract aspects of the nullspace.

 _“Sans,”_ he said quickly, trying to prioritize all the questions that were clambering over the top of each other. Even if he wouldn’t remember, he had to know. _“Is He Safe?”_

“Tricky,” the Other commented. “At Your Differential He Is Nonexistent—Between This Universe And The Old. And At My Differential It Depends, Entirely, On Which Timeline He Finds Himself In. Safe?” the Other mused. “I Can Say This For Certain: You Will Meet Him Again.”

Gaster could hardly attempt to puzzle out what the Other meant by differentials and timelines, but he could feel the tide of the void pulling him back, and knew he didn’t have time to ask for elaboration.

 _“And His Brother?”_ he asked.

“Papyrus,” the Other chuckled, “Is As Resilient As Ever. Yes, You Will Meet Him Again, Too.”

_Good._

Gaster was out of time.

 _“And You,”_ Gaster said, fighting to stay with the last of his will. _“Who Are You?”_

The Other watched him leave, its soul growing faint as they parted. “You Know Who I Am.”

Gaster did.

_“You’re—”_

 

\---

 

“—Me.”

Gaster blinked, staring down at his hands. What had just…

“...Gaster? D-doctor Gaster? Are you alright?”

Gaster looked up, meeting Alphys’s concerned gaze.

“I-I was asking if you’re r-ready,” Alphys said. “But y-you seem kind of out of it…”

Right. Alphys had just been about to remove his IV—no, that wasn’t right; he distinctly remember her removing it. He must have had another one of those strange time jumps. Like a skipped record, everything suddenly jumping back a few seconds in time. How many times had he noticed it now? Before, he’d been aware of it happening, though this time something seemed… off. Hazy.

There was a window. And someone else….

“...Gaster?”

The thoughts dissolved before they could coalesce. Gaster shook his head.

“Right. Sorry, Alphys. At Your Leisure, Doctor.”

Sparing him another concerned look, Alphys nonetheless reached inside Gaster’s exposed rib cage. Gaster tensed minutely as the scientist gently took his soul in her claws. Not in one of his finest moments, he could recalled ripping the IV from his soul. The pain had been excruciating yet brief, due to the first time skip he could distinctly recall. Obviously Alphys would be more gentle than that, yet the memory itself seemed to have been what triggered his most recent jump. Gaster grimaced, hoping it wouldn’t happen again.

With a faint pinch, the IV came free.

And… nothing glitched.

“Well,” Alphys said, taking an awkward step back. “I, um. I guess you’re set. Oh! Um, I brought you some clothes, too, now that you’ll be out of bed. And, um, I think I found your prescription, or s-something close...”

Gaster relaxed, absently taking the pile of clothes that Alphys brought over. That had gone better than expected.

“Thank You, Doctor,” Gaster said, opening the glasses case to examine the pair of spectacles inside. He lifted the glasses up to his face to test them out, and it occurred to him that wearing the lenses would prove difficult without ears and a nose. Well, he was well-used to improvising. “Your Hospitality Is Always Appreciated,” he added.

An orange discoloration spread across Alphys cheeks, and if Gaster had been even remotely socially aware he might have recognized it as blushing.

“Oh, o-of course,” the doctor stammered. “I, um, also brought some of the books you asked about. The, um, ones on m-magic. I couldn’t f-find any of the math texts you were looking for...”

“No Matter,” Gaster said. “The Ones On Magic Will Be More Useful, Anyway. I Believe I Remember Enough Of My Own Education To Make Up For…” Gaster drifted off as something nudged at his subconscious. “Actually,” he said, “Do You Have Any Fiction?”

“Fiction?” Alphys repeated.

“Sci-Fi And The Like,” Gaster elaborated.

“Oh! Um, yes, of course.” Alphys smiled weakly. “It’s way more common for those sorts of books to fall down here than text books, anyway. Um, was there anything…?”

“A… A Book By Kurt Vonnegut,” Gaster said, wondering why it had suddenly come to mind. “ _Slaughterhouse-Five_ , I Think, On The Off-Chance You Have It. Actually,” he said, changing his mind, “Don’t Bother. Perhaps I’ll Just Accompany You To Browse The Collection The Next Time You Visit.”

“Oh… okay,” Alphys agreed, tilting her head in slight confusion.

Gaster was somewhat baffled himself. He didn’t know where that request had come from, and given the circumstances he certainly didn’t have time to be indulging in fiction. As Alphys busied herself with packing up the medical equipment, Gaster picked up one of the tomes on monster magic and flipped the cover open to the first page.

It probably didn’t mean anything, he reasoned. Perhaps an old memory, stirred by talk of Alphys’s books. Nothing to dwell on.

Certainly nothing important.

 

 

 

**Notes for the Chapter:**

> Sorry this chapter took so long to get out! There were, like, hurricanes and stuff. 
> 
> It occurred to me that I never explained where Gaster's Followers fit into the story, so I figured now was as good a time as any to address that.


	6. Ultima Thule

**Summary for the Chapter:**

> Gaster starts to investigate his magic.

Now that, in Alphys own words, Gaster “appeared to be stable,” her visits to the infirmary became less frequent. Nurses delivered clothes and a few books on her behalf—along with meals.

With the IV removed, Gaster was quickly and forcefully graduated to solid foods. The first time, a bird-like monster delivered a sandwich and glass of water. Gaster stared at the plate.

“I’m Meant To Eat This?” he asked.

The nurse cocked an eyebrow. “Well you’re not meant to play with it.” 

Gaster shot the monster an unimpressed glare, which might have been more intimidating were he not a patient. Returning his attention to the food, he couldn’t help but hesitate. Could he even  _ eat? _ He supposed he wouldn’t have been sent food if Alphys thought he couldn’t, but… Well, he supposed there was only one way to find out. Predicting the water would be inconvenient to clean up should his experiment fail, Gaster settled on trying the sandwich first. 

Gaster stared at the food for a moment before finally tearing off a corner of the sandwich. How would this work, exactly? His lower jaw had no bottom—not to mention the fact that he lacked a tongue, throat, stomach, digestive tract… The list could go on.  

Gaster huffed a laugh, amused with himself. Once again, he was expecting things to operate logically. Trying to think things through in this reality was getting a bit futile, wasn’t it?

Before the nurse could tell him to hurry things up, Gaster popped the bread and meat in his mouth. Despite all reason suggesting otherwise, the food stayed put as he chewed and then swallowed. Gaster looked down into his chest, waiting to see what would become of the masticated sandwich, but somewhere between his mouth and throat the food appeared to have vanished. Gaster tried again with similar results. 

“Fascinating,” he said, starting a third trial. The nurse, still waiting for him to finish, did not seem nearly as impressed. 

“You’re a rather strange fella, aren’t ya.” Her tone made it clear this wasn’t a question.

Gaster resisted the temptation to roll his eyes. Technically, her assessment wasn’t entirely wrong; he was certainly strange to this world. 

“Thank You, For Your Most Astute Observation,” Gaster replied instead, picking up the glass of water. Like the sandwich, the water that entered his mouth never reached his ribcage. Even the nurse’s comments couldn’t dampen the delight Gaster experienced from running these (admittedly mundane) experiments. How did it work? Was the magic deconstructing the food? What else could magic deconstruct? 

Despite his sarcasm, the nurse chuckled. “Seeing as you’re occupied and all, I’ll be back to check on ya in an hour. Try not to choke on anything in that time.”

“Your Concern Is Noted,” Gaster said, hardly paying attention. The nurse shook her head, and was smiling to herself as she left. 

The sandwich and water, unfortunately, proved to be a limited resource that exhausted itself all too soon. Gaster could have easily spent the rest of the morning experimenting with his food, (alright, so perhaps he  _ was  _ playing with his food,) but now that it was gone he had other matters he was eager to attend to. Donning the pair of reading glasses Alphys had been able to provide (after a bit of fiddling he was able to hook the ends through a gap in his cheek bones—which he expected were meant for his jaw muscles—in order to secure them to his face,) and pulled out the first of several text books he intended to read. 

Alphys had been right about not having many scientific texts; she’d scraped together a book on calculus, a partly-completed undergraduate physics workbook, an electrical handguide, and an advanced text on chemical applications for computational analysis. Altogether, Gaster found them next to useless. It seemed his scientific exploits on this world would have to rely on the knowledge he had brought with him. Whatever disappointment he felt with the textbooks, however, was short-lived the moment he cracked open the first magical tome. Now here was something  _ new _ . 

Gaster didn’t notice when the nurse returned to take his plate and empty glass away, nor did he hear her assurance that she’d be back again that evening with dinner. In fact, Gaster continued to read, wholly insulated from everything beyond the pages of his book, until he turned the last page and was forced to slowly rouse from its depths. There was another glass of water and plate of food by his bedside, long since gone cold. The lights were dimmed, though not out, and the facility seemed quieter. Gaster considered this for a moment, idly wondering about the time, before picking up the second text on magic, turning to the first page, and starting again. 

That night, the scientist did not sleep.

 

\---

 

Small, purple bones sprung to life between Gaster’s fingers, emitting a soft glow that illuminated his hands. Gaster gestured and the constructs twirled and grew, following his concentrated intent. The cluster moved towards the book he’d laid out before him, fumbled around the cover until one of the bones caught, and flipped the text open. Gaster let out a breath as he allowed his focus to slacken.

“Y-you’ve been practicing,” Alphys noted. 

“Yes, Well. I Thought It Would Be Best To Avoid A Repeat Of The Events Surrounding Undyne’s Confrontation,” Gaster said. 

“Oh, y-yeah, that makes sense,” Alphys nodded, having the decency to look remorseful. Her attention, however, remained on Gaster’s constructs as they continued to fiddle with the book. “You caught on r-really fast.”

Gaster sat back, making only a superficial attempt to hide his smugness. “The Text On Magic Theory Was Useful, Though Perhaps Somewhat Elementary. If You Have Any More Advanced Texts On The Subject, I Should Like To Take A Look.” 

Alphys’ attention snapped back to Gaster. “You read it already?” 

“I’ve Finished  _ A Modern Theory On Magic  _ And  _ Soul Classification Guide _ , And Am Part Way Through  _ A History Of The Underground _ , Though The Last Feels A Tad… Amateur,” Gaster said. “Regardless, I Was Hoping To Browse Whatever Other Material You Had On The Topic.”

Alphys’ eyes gradually widened as Gaster spoke. “Oh, w-wow, okay. I wasn’t expecting you to finish them so fast. Um, alright…” Alphys wrung her hands, her glazing sliding away from Gaster in a way he was beginning to recognize as a tell that she was deliberating over some matter. After a moment of silence, she seemed to come to some decision. 

“Do you, um, feel well enough to walk?” 

“Of Course,” Gaster said, fighting to sound neutral. How long had he been down here without seeing anything past the end of his bed? There was a vague memory of damp moss and blue, luminescent flowers, but… He was sure the Underground held so much more to see and learn. Gaster was not predisposed to passivity. “Now? Are We Going At This Moment?”

Perhaps he hadn’t sounded as casual as he had intended, for Alphys broke into a nervous chuckle. “Y-yeah, I think I have some time now. A-and you can’t stay here forever, especially that you’re now, um, healed.” Alphys’ nose wrinkled in thought. “I guess we’ll have to find somewhere for you to stay, too…”

Gaster, meanwhile, had banished his magic constructs and set the texts aside. He was fully clothed, finally—dressed in a patchwork of clothes that managed to stay on his skeletal frame, including sneakers, a collared shirt, and a pair of sweatpants that were cinched awkwardly above his hips. Not the most fashionable of attire, but it would do until he found something more suitable. Alphys had promised she’d check the dump regularly for clothes that aligned more with his taste, though Gaster wasn’t entirely sure what she meant by this, and wasn’t particularly bothered by the mismatching outfit regardless. How could he be worried about clothes when there was a world full of magic to explore?

Alphys emerged from her fretting as Gaster stood and habitually began to roll up his sleeves. Something unreadable passed over her face, but flitted away before Gaster could comment. 

“Where Are We Going?” Gaster asked when Alphys still hadn’t spoken. 

“Oh!” The doctor jumped. “Um, r-right. I was thinking the royal archives. If there’s any more human books, they would be there. There’s also a lot more m-magic texts than why I have. My personal collection is mostly l-limited to, um,  _ other  _ genres.” 

Gaster almost asked Alphys to elaborate before deciding it was irrelevant. Instead, he simply nodded. “That Sounds Reasonable. Lead The Way, Doctor.” 

An awkward smile returned to the lizard monster’s face as she pulled the bedside curtain back, and showed Gaster out the infirmary’s door. Their path wound through a series of hallways and rooms filled with monsters going about their business, many of them wearing labcoats and each stranger than the last. Though Gaster had begun to grow used to their presence during his time spent in the infirmary, it was still surreal to be surrounded by so many monsters at once. Nervousness stirred in his bones, but he consciously brushed the instinct aside. No one was giving him or Alphys a second glance; he was in no danger here, Gaster reminded himself. 

So long as they didn’t think he was human.

At last reaching the entrance to the building, Alphys paused at the door to turn and give Gaster a reassuring smile. 

“U-um, I know it’ll be different from what you’re used to, but… Um, I guess, welcome to New Home.” 

The ceiling—given the Underground’s name—Gaster had been expecting. The rest of it… well, Gaster wasn’t sure  _ what  _ he had been expecting. 

The hospital was situated on a shelf that overlooked much of the city that clustered below, buildings packed together like too many matchsticks shoved into a box. Though the cave itself was dark, the town was bright with lights of every color and size; Gaster could only imagine what powered the city, assuming what he saw was even of an electrical nature at all.  Thousands of monsters must reside there, and Gaster could see them moving about the streets, distant and teeming. Towering over the city, on the same overlooking shelf as the hospital itself, was a castle made of white stone. It was in that direction Alphys gestured, prompting Gaster to move when he realized he was staring. 

“Do You Live Down There?” Gaster asked as they walked. He was looking in all different directions as he spoke, trying to take in every monster and strange, new sight they passed on the trail. 

“Technically,” Alphys said. “B-but I spend so much of my time at the lab that it might as well be my home. Sometimes I even fall asleep there, heh.”

Gaster smiled, familiar with the situation. “I Presume The Hospital Is Not Your Only Place Of Work?”

“Oh, n-no,” Alphys admitted, slipping through the crowd with enviable ease. She occasionally had to stop to keep Gaster from falling behind. “I d-don’t actually work at the hospital. Um. I w-was brought in as a specialist, due to my experience with soul research…” Alphys absently gestured behind them. “I usually work in a lab in Hotland.” 

Gaster cast a glance back, then stopped in his tracks to get a better look. Though he had no clear line of sight, the wavering, red-orange glow of the cavern and was unmistakable. Gaster then looked up and around, reevaluating the structure of the Underground.

“Alphys,” Gaster said.

“O-oh!” The monster hurried back to Gaster. “Sorry, I d-didn’t see that you’d stopped.”

“Alphys,” Gaster said again. “Are We... Inside A Volcano?”

Alphys followed Gaster’s gaze up towards the ridged ceiling. “Oh, um, yes, I s-suppose that’s accurate. B-but! These chambers are completely d-dormant. Um. Just H-hotland has exposed magma.” She looked back towards the distant red glow. “I’ve, um, b-been trying to find a way to harness its geothermal energy, actually. M-maybe use it to power the rest of the Underground.”

Gaster hummed in thought. “Interesting Idea,” he granted. “I Should Like To See What Those Plans Are, If You’d Allow Me. I Spent A Considerable Amount Of Time Trying To Decide How Best To Harness Enough Energy To Power My Lab, In Fact. I Might Have Some Insight Into The Affair.”

“R-really?” Aphys asked. Her eyes appeared wide behind her spectacles. “Th-that would be great! I-I mean, if it’s not a bother.”

Gaster smiled. He was still technically her patient, yet he felt like he was being treated more like a colleague. Not that he was complaining. The prospect of studying magic and engineering in tandem was attractive—and if he were being honest, the presence of the volcano was more than a little motivating for finding a way out of here. These chambers might not have seen magma in many millennia, but if there was exposed magma nearby then the mountain was anything but dormant. Whether it would be through discovering a way to break the barrier, or through reinventing his time machine, he didn’t intend to spend the rest of his days in this ticking timebomb. 

For that, however, he would need resources. Time, materials, knowledge… Gaster looked at Alphys thoughtfully.

“Of Course,” Gaster said. “I’ve Little Else To Do, After All. But Perhaps, First, It Would Be Beneficial To Proceed To The Archives…?”

Alphys gave a start. “R-right!” she agreed. “It’s not far from here. Just, um, l-let me know if you need to take a break…”

Despite Alphys’s offer, Gaster managed the rest of the trek well enough. He’d never been the most athletic of men in the first place, but it seemed he’d recovered enough stamina to complete the trip without needing to rest.

The archives turned out to be inside the castle itself. Gaster felt somewhat out of place in such a gaudy abode, though his presence was largely ignored with monsters greeted and nodded towards Alphys, who was leading the way. Gaster realized her station commanded more respect than he’d initially given her credit for, and his respect for the society increased; any community that regarded science in such esteem couldn’t be all bad. 

The archive itself was much smaller than any libraries Gaster was used to, but it was about what he had been expecting. Gaster had more texts in his studies at home, though he could hardly be disappointed; after Alphys showed him the rather small collection of human books, he quickly turned his attention the magical tomes. 

It was like stepping foot into Alexandria. Never could he have imagined he would be handling texts that hadn’t been seen or touched by another living human—or any human, for that matter. How old were these books? How much secret knowledge did they hold? Unable to wait until he was back at the infirmary, Gaster began to leaf through pages of the books as he pulled them off the shelves. It was difficult to decide which ones were of the most importance at a glance, and despite his best attempt to show prejudice, his “keep” pile was steadily growing to impractical heights. Alphys giggled when she noticed this, drawing Gaster out of the latest text he’d fallen into. 

“Y-you know, we can always come back,” Alphys said. 

Gaster brightened at the suggestion. “Ah, Right, Of Course. Forgive Me.” He turned to look at the books he’d set aside; the stack was almost as tall as Alphys herself. “I… May Have Gotten Carried Away.” 

Alphys gave him a knowing smile. “I-it’s okay. I understand what that’s like. S-sometimes when I find something I like to read in the dump, like a new manga, I get really excited and then I started digging around more incaseanyothervolumesfelldownwithitandifI’mreallyluckythensometimesI’mabletofindmorewhichisjustlikethebestfeelingbecausethenIknowforthenextcoupleofdaysI’llhaveanewworldtoescapeintoandooooohhh stars I’m rambling again, I’m so s-sorry.” Alphys blushed, clasping her hands over her mouth.

Gaster hadn’t gotten much of that, but enough to amuse him. The fact that her stutter had stopped hadn’t escaped him, either. When it came to her passions it appeared she was capable of displaying confidence after all. Gaster absently wondered if he could find what other subjects made her tick. 

But that was an experiment for another time.

After reluctantly reshelving over half the texts he’d set aside, Gaster and Alphys made their way back to the hospital. 

“I’ll, um, start looking into some places you could stay in New Home,” Alphys said as they approached the infirmary. “You’re d-definitely clear to leave here, just, um, as soon as you have a place to go.” 

“Thank You, Alphys, I Appreciate That,” Gaster said. “I’m Sure Dealing With My Unique Situation Has Not Been Easy For You.”

Alphys’s eyes widened. “Oh, n-no! Not at all! It’s actually k-kind of exciting, really. Evidence that t-time travel and the multi-worlds theory exists—I still have so many questions…”

“That Makes Two Of Us,” Gaster said, carefully trying to steer the conversation away from what those questions might be. “Perhaps We Can Help Each Other With The Aspects Of Science That We Are Each Most Familiar With. It Should Be Interesting To See How Our…  _ Diverse  _ Backgrounds Can Be Combined.”

“Of course!” Alphys nodded along. “I, um, can show you around the lab maybe. L-later this week. If you wanted to see what I’m c-currently working on.” 

That was easier than Gaster had anticipated. “Certainly,” he agreed. “I Should Like-”

“What is  _ he  _ doing out here?” 

Gaster sighed. He didn’t need to turn around to know which monster had just caught sight of them. 

“U-Undyne!” Alphys exclaimed, her face noticeably growing pale. “W-we were j-just—um, just getting some reading material—”

“Why’s he outside of his room?” Undyne demanded, her boots ringing as she stalked down the hall. Alphys shrunk back as Gaster finally turned around, looking the guard up and down, unimpressed. 

“Why? Am I Not Allowed To Leave?”

“Not without supervision,” Undyne said, addressing Alphys rather than Gaster. “We  _ talked  _ about this. You were supposed to call me.”

“I’m s-sorry,” Alphys said. The poor scientist truly looked miserable. “I w-wasn’t thinking. It w-was just a t-trip up to the royal archives-”

“The _ royal archives? _ ” Undyne snapped. “You took him into the  _ castle? _ Stars, Alphys, what were you thinking—” 

Something was buzzing at the back of Gaster’s mind, familiar and unsettling. It wasn’t irritation—though he was certainly irritated with Undyne, (and felt a little bad for Alphys as well.) The sensation was a strain of caution, almost, one that was impossible to ignore. The insistent prodding was reacting to Undyne’s anger and stirring magic. It took Gaster a moment to recognize it as his own magic—the kind he often thought he’d imagined. This was different from the magic he used to form bone constructs; this was something more subtle. He could recall using it before, when he was still half delirious from his adjustment to this world, but he’d never quite figured out exactly what it had done. There were some rather unsettling inconsistencies in his memories at those points. Just thinking about it made the cracks in his bones itch. 

Gaster tried to focus back on the conversation Undyne and Alphys were having, but his magic spoke louder. It wanted to be used. The last thing Gaster wanted was to antagonize Undyne further with a display of magic, but the more outspoken the guard became, the more the sensation was becoming hard to ignore. If nothing else, Gaster reasoned, he needed to look at it. Examine it and, if need be, contain it. 

Frowning with concentration, Gaster mentally reached out for the strange, separate magical reserve. Somehow, Undyne seemed to notice this. 

“Hey, what are you—”

As Gaster took hold of the magic, it took hold of him. There was a tight pulling sensation, a pain that wrenched through the scabs in his bones, then sudden, cold, blackness. There was a moment where he thought he ought to recall something in this place, but the inclination was whisked away just as quickly as everything blinked back into sight once more. 

Gaster sucked in a breath at the fire that was running through his bones. It felt like he’d just been pulled in every direction at once. What had just…?

“… at all!” Alphys was talking. Undyne was gone. Gaster looked around, collecting his wits and confirming he was still in the hospital. “It’s actually k-kind of exciting, really. Evidence that… um… Gaster?” Alphys paused. “Are you okay?”

Gaster’s attention snapped back to the doctor. “Ah, Yes, I’m Fine…” His eyes trailed down to one of his hands, still clutching the stack of books. He was unsurprised to see several of the old wounds had opened, some leaking drops of blood. “Actually… It Might Be Best If I Got Some Rest. A Lot Of Walking Today, And, Er, So Forth.”

Gaster hastily stepped back into the infirmary, pointedly avoiding Alphy’s baffled face. 

“A-are you sure?” Alphys said. Then her eyes widened. “Oh! Y-you’re bleeding again! What—”

“It’s Fine, As I’ve Said,” Gaster insisted, shifting the books to one arm so he could reach for the door. Alphys got there first, wedging herself in the doorframe and holding it open. 

“I— I know y-you still have some secrets y-you’re keeping from me,” Alphys started, taking a deep breath, “but I’m s-still your doctor a-and—”

“Hey, Alphys!” 

Alphys jumped as her name was called, spinning back towards the hallway. “U-Undyne!” she squeaked. Her head halfway turned back towards Gaster as she hesitated, then she hastily pulled the door shut. Muted, through the wall, Gaster could hear her ask, “W-What are you doing here?”

Gaster slumped, letting out a breath. He remained standing at the door as his mind worked, trying to decide if what he just thought had happened had, in fact, happened. 

It wasn’t impossible, of course. He had invented a timemachine after all. But could magic even… had he really just...?

Gaster let out a shaky laugh as he headed over to his cot and deposit his books at the bedside table. He sat heavily, looking at the reopened wounds in his hands. The magic appeared to be stressful on his body—but it was also proof that something had happened. That he hadn’t imagined it. Gaster laughed again, removing his glasses to rub the bridge of his nose. 

“Of All The Things To Find Unbelievable,” Gaster murmured, distantly amused with himself. It even made sense, in a way. He traveled through space and time to arrive at this world, and his magic was formed during that transition. Why wouldn’t it be connected? 

He could go back in time. Gaster paused, trying to let that thought sink it.

Did this mean he could go home?

“No,” he told himself. “It Can’t Be That Easy.”

“Golly, it sure didn’t  _ look  _ easy.” 

Gaster jumped to his feet, ignore the burning sensation that tore across his limbs at the sudden movement. He thought he’d been alone, and even now the room appeared to be empty.

“Does it always make you bleed?” This time, Gaster located the source of the voice. There was a yellow flower at the foot of his bed, smiling up at him. 

“Wow,” the flower giggled. “That is  _ super  _ inconvenient.”

 

 

**Notes for the Chapter:**

> Really sorry about this, but the next chapter probably won't be up until sometime in December. I'm doing NaNoWriMo this month, so not a lot of writing outside of that project is going to get done.


	7. When Fighting Monsters

**Summary for the Chapter:**

> Gaster and Co. have a chat.

**Notes for the Chapter:**

> Sorry this chapter took so long to get out. After NaNoWriMo there were finals to worry about. Now that I've got some time off, however, I'll try to resume regular posting. 
> 
> Thanks for reading.

 

Gaster’s eyes narrowed.

“What Are You?”

“Wow, _rude_ ,” the flower said.

“What Do You Want?”

“I get the feeling you’re not really one for small talk,” the flower said.

“What Are You Doing In My Room?” Gaster said, not to be deterred.

The flower frowned. “Golly, you’ve got a lot of questions. What if I said I was cleaning flower? All houses have cleaning flowers, you know.”

Gaster stared at the flower for a moment. “I Don’t Believe You.”

“Are you _sure?”_   the flower pressed, a wide smile cutting across its face. “Because man, not knowing about something as common as cleaning flowers is _pretty_ suspicious.”

Gaster didn’t say anything, and just continued to stare.

The flower’s smile turned into a smirk. “Heh, got to hand it to you, you’re not as stupid as I thought. Still, you’ve got a lot of tells. Do you really think Undyne buys that ‘I lost my memory’ crap?”

Slowly, Gaster shifted his posture, standing up straight and folding his arms across his chest. “I Think It Would Be Best If You Left Now.”

“Left?” the flower exclaimed. “But I’m just trying to do you a favor, friend!”

“Somehow,” Gaster said, “I Find That Doubtful.”

“I know, sometimes I surprise even myself,” the flower said, smiling sarcastically. “But this thing you’re dealing with’s not your typical strain of magic. Trust me, no one here’s going to understand, not even Alphys.” Gaster glanced towards the door as Alphy’s name was mentioned. So far, however, it seemed Undyne was keeping her preoccupied. It wasn’t difficult to overhear the Captain’s voice through the wall. “I, however,” the flower continued, “have some experience in the area. Could even give you some tips.”

Gaster’s gaze went back to the flower. He didn’t like this conversation. The only way the flower could know as much as it did was if it had been watching him over the past few weeks. As much as it claimed it only wanted to help, Gaster doubted its intentions were as benign as it insisted. Something about the creature’s presence rubbed him the wrong way. Gaster couldn’t put his finger on it but something… something wasn’t right.

As much as Gaster prided himself as a man of reason, he also knew when to trust his instincts.

“I Have No Idea What You’re Talking About,” Gaster said levely.

The flower’s smirk took on an unkind edge. “You _sure_ about that?” the flower pressed. Gaster remained silent. “Well, then,” the flower said. “Maybe we just need a _demonstration_.”

Too fast for Gaster to follow, a blur of green speared up through the tiled floor, closely followed by a small jolt of pain that sparked through his soul. Gaster gasped, staggering back from the impact as he raised a hand to his chest. His hand bumped into something that shouldn’t be there, sending another lance of discomfort through his soul and bones, and when he looked down it took him a moment to comprehend the sight. A green vine had stabbed through his chest and crumpled against his soul. Even as he watched one of his cracked ribs sloughed off a layer of dust, and the vine maneuvered to wrap around the soul it had failed to pierce through. The movement was disturbing and invasive, and the sickened shiver it induced in Gaster broke him out of his initial shock.

Magic roared through him, fueled by anger and indignation. Gaster didn’t even try to hold back or understand what the magic would do, and though it ripped his wounds open anew he hardly felt it or cared. The doctor let the instinct consume him, let the energy build to an overwhelming pressure, and just as it became too much for him to hold—all in a matter of seconds—Gaster unleashed the wild magic.

Violet light flashed through the room. Heat coursed through Gaster’s soul and a sharp sting cracked through his bones. The light vanished at once—there was a brief, familiar blackness—and with it went a portion of his stamina. As the sensation dispersed Gaster reached out to steady himself with his bedside table, letting out a pained hiss as several of his scabs throbbed with the telltale pain or reopened fractures.

“Jeez, that’s really not easy on you, is it?”

Gaster rounded on the flower, his magic flaring to life once more as his frustration spiked.

“Whoa, there,” the flower raised a leaf in a placating gesture, “you really want to go through that again?”

“You _Attacked_ Me,” Gaster snarled, letting the magic build.

“Um, yeah, that was sort of the point, buddy.” The flower rolled its eyes. “And I _remember_ attacking you. How else was I going to prove that I’m aware of the loads?”

Gaster hesitated, still letting his magic build. Remember? It couldn’t be talking about…

“Hm, though it’s not really a load, is it?” The flower seemed to be musing to itself more than addressing Gaster. “They’ve all been really short. Thirty seconds, tops? More like a record skip. Kinda pathetic, really.”

Gaster, still quite furious, managed to clamp down on his magic, taking a second to let out a breath as he reeled it back within his control. Another time jump wouldn’t achieve anything—apart from hurting himself more—and there were more constructive ways for his magic to be used. Frustrated that he had allowed himself to give in to his emotions so easily, Gaster collected himself and repurposed the roiling store of magic, summing an array of purple bones to aim at the flower instead.

“If You So Much As Move The Wrong Way,” Gaster said, “I Will Not Hold Back.”

The plant spared the constructs a brief glance, but didn’t seem impressed. “If it’s a fight you’re looking for, the encounter will be embarrassingly short. I’m not exactly packing the big guns here.”

“Wha—You— _I_ Am Not The One Trying To Pick A Fight,” Gaster spluttered, his temper flaring once more. “You Tried To _Kill_ Me!”

“Oh _please_ ,” Flower said. “Stop being so dramatic. I barely scratched you. Come on, with HP like that? Looks like you’re doing more damage to yourself than I ever could. Best I can manage is a good startle. Heh!” The flower smiled once more, the expression lacking any kind of actual mirth. “Guess I did a good job, huh?”

Gaster warred with his emotions for a moment, fighting down successive waves of disbelief, anger, and an almost overwhelming urge to drag a hand down his face. He took a steadying breath. Held it. Counted backwards from ten.

“What,” Gaster said, “Do You _Want?”_

The flower let out a long, dramatic sigh. Gaster waited, even as it began to try his patience. “I’ve already _told_ you what I want.”

Gaster thought back on their conversation (if he could call it that.) “My Magic,” he said. “You Said You Know About It.”

“Now we’re getting somewhere,” the flower grinned.

“How?”

“How do I know about it?” the flower clarified. “I guess you could say I’ve got some experience in that same type of magic myself. Well,” the flower considered. “Not _exactly_ the same type of magic. Perseverance, right? Guess that explains why it’s so much weaker than Determination. Only much good for self preservation, looks like.” The flower shook its head. “No _finesse_.”

Gaster frowned but kept his bone constructs level. “You’re Capable Of The Same Magic? Prove It.”

“Gee, I’d really love to,” the flower said, “but unfortunately that’s not possible right now. Looks like the Underground ain’t big enough for the bother of us.” It smirked at its apparent joke.

“Explain,” Gaster said.

The flower approximated a shrug with its leaves. “Not much to explain. Only one time-traveller’s allowed at a time, I guess. I stopped being able to reset the moment you arrived here.”

“Why?” Gaster asked.

“Why?” the flower repeated. “Why would _I_ know that? I’m just a flower.”

“One That Seems To Know An Awful Lot About Magic,” Gaster observed.

“Heh.” The flower’s smirk turned sour. “Let’s just say I’ve had a lot of time to figure things out.”

A chill ran through Gaster. Just how old was this monster? How much time had it re-lived? Something made him doubt he’d get a straight answer to either of those questions.

Yet, this was the closest to answers that he’d come. Despite its dubious nature, the flower knew things Gaster didn’t—things he desperately wanted. If he could learn more about his magic, if there was some way for it to be honed, there was a chance he could discover what had happened to Sans and Papyrus, or possibly even prevent the accident in the first place. Gaster was not one to turn down valuable information because it came from an undesirable source.

And the source _was_ undesirable. Someone who was trustworthy did not follow up their introduction by launching into an attack—even if it was, as the flower claimed, for demonstration purposes. Gaster very much doubted that. What had been the real purpose of the flower’s aggression? To confirm that Gaster was really capable of time jumps? To test his magic—or temper?

Or, it occured to Gaster, the likelier option was that it hadn’t been a test at all. Perhaps the flower’s attack really been an attempt on his life. If the flower was truly unable to use its ability with Gaster around, its most obvious course of action would be to eliminate the factor that was overriding its magic. If the attack succeeded, the problem was solved. If it failed, the aggression could be explained away. The more Gaster thought about it, the more he became sure that this was the case.

With a concentrated amount of willpower—and actively ignoring the strange instinct that told Gaster this creature was _wrong_ and _dangerous_ —he let his bone constructs fade away. The flower raised a curious eyebrow as Gaster took a step back and straightened out his shirt. He had to play this carefully.

“I Believe You,” Gaster said. “You’ve Demonstrated You’re Cognizant Of The Time Jumps, And You Appear To Be Knowledgeable About The Magic’s Nature. Even If You Can’t Demonstrate That You Are—Or Were—Capable Of The Magic, I Will Choose To Believe You When You Say That You Could. As Such, I Am Willing To Work With You If You Are Offering Advice. However, There Is Something I Would Like To Know, First.” Gaster paused, trying to read the flower’s expression. “What Is Your Motivation In Helping Me?”

Suspecting the true answer was likely something along the lines of ‘to learn your weakness’ or ‘to assassinate you,’ Gaster expected the flower to hesitate as it sought out some other believable explanation. He was surprised, however, when its answer was immediate.

“Because this is all just so _interesting_ ,” the flower giggled. “I can’t _wait_ to see how everything is going to unfold. _Golly_ , it’s been a long time since something new happened!”

Gaster, caught off guard by the response, didn’t know what to say. Had he completely misjudged the flower’s intent?

“Anyway,” the flower continued before Gaster had recovered, “Sounds like the lizard’s about done talking with Anger Management Issues, so it’s time for me to go. See you around, Bonesy!”

“Gaster,” he corrected automatically. Did the flower not want to be caught talking to him? “Hold On—Wait—” Gaster said as the flower began to lower itself into the cracked tile. “How Will I Get In Touch With You?”

“Oh,” the flower said. “Don’t worry about that. _I’ll_ get in touch with _you_.”

“And Your Name?” Gaster asked.

“Sure took you a while to ask,” the flower winked, sticking out its tongue. “It’s Flowey. Flowey the flower!” And with a faint _pop_ it disappeared into the floor.

Gaster was still staring at the thin crack in the tiled floor when he heard the door to the infirmary open.

“U-um. Hey.”

Gaster was delayed in turned to face Alphys, his mind still processing the encounter he had just undergone. The doctor hesitated in the doorway as her eyes darted around the room.

“Um. Is anyone else here? I th-thought I heard you t-talking to someone.”

Should he tell her? Flowey had obviously wanted to avoid being caught here. Did Alphys know anything about the creature? Or would admitting its presence only aggravate the flower and cause it to change its mind?

Best to play it safe until he knew more.

“No,” Gaster said. “I Was Just Talking To Myself. Was Everything Alright With Undyne?”

“Oh, er, yeah,” Alphys said. A pause. “You, um, overheard?”

“She’s Not The Most Subtle Of Personalities.” Gaster offered a small smile, allowing himself to relax for the first time since the flower had shown up.

Alphys returning the smile, chucking softly. “Yeah, sh-she’s definitely something. But it was p-probably for the best that you went in when you did. Um. I s-sort of forgot before, but she doesn’t want you walking around unescorted. Sorry.”

“It’s Fine,” Gaster said, narrowly avoiding saying ‘I’m Aware.’ Flowey had said Alphys wouldn’t understand the time jumps. Certainly she wasn’t aware of them, but would she believe him if he told her? Probably.

 _Should_ he tell her?

Hard to say. Undyne was already proving to be a thorn in his side, and though Alphys had backed him in the past, he wasn’t sure how much would be _too_ much before she felt she had to go to the Captain with what she knew. Time magic, from what he’d learned so far, wasn’t supposed to exist. Or at least, none of the texts he’d read on magic had mentioned anything close to it as a potential ability. If this ability was due to his non-monster origin, would it be enough to tip Alphys off that he wasn’t, in fact, a monster?

For that matter, what did all this say about Flowey?

“...Gaster?” Alphys prompted after a moment of silence. “Um, you got really quiet…”

“Lost In Thought,” Gaster said. “Sorry. Perhaps A Day Of Exercise And Library Scrounging Was Pushing My Limits. I Think I’ll Spend The Rest Of The Evening With The Books.” He’d almost forgotten about the texts in the midst of everything else.

“Oh, um, yeah, g-good idea,” Alphys said. Glancing towards the door, then back into the room, she continued to linger. She fidgeted with the cuff of her lab coat.

“Is There Something Else?” Gaster prompted, once it was clear it was going to take some time for Alphys to figure out whether or not she wanted to speak up. The doctor startled at Gaster’s question, but nodded quickly.

“I, just, I know it sounds a b-bit silly, but… I just had this feeling, and, um… I just wanted to make sure everything’s okay? That _you’re_ okay?”

Gaster smiled in what he hoped was a reassuring manner. “I Appreciate The Concern. Of Course, Alphys.” _Keep your friends close,_ he thought as he sat down on his bed. “Everything’s Fine, I Assure You.” As he bent over, his gaze briefly flickered over the crack in the tile. _And your enemies closer._


	8. Terminus

**Summary for the Chapter:**

> Terminus: a final point in space or time--also the Roman god of boundaries. 
> 
>  
> 
> [A chapter in which Alphys and Gaster have a talk. ](https://www.youtube.com/watch?v=zGbNbn8tB5k)

Alphys woke up to darkness. She flailed for several seconds, briefly entangled in her blankets before she kicked the comforter aside and flopped back onto the mattress. Alphys panted, blinking against the black and wondering what had jolted her awake. A nightmare?

Alphy’s phone buzzed, and the jingle to _Mew Mew Kissy Cutie_ started up again. Groaning, Alphys rolled over to grope blindly for her phone. After knocking a stack of manga off the bedside table she found the device and brought it up to her face, squinting blearily at the display.

“Gaster?” Alphys croaked, picking up. “What _time_ is it?”

“Time?” Gaster echoed. “Oh, I’m Not Sure. Is It Late?”

“Early,” Alphys sighed, sitting up. “Is everything okay? What’s going on?”

“Everything’s Wonderful. Excellent, In Fact. Sorry About The Time. Do You Have A Moment?”

Alphys rubbed her eyes and yawned. “Now?”

“That Would Be Ideal. It’s About The Barrier.”

Alphys sat up straight, completely awake. “The barrier? You have an idea? Th-that’s amazing! Where are you now? Sh-should I meet you in the lab?”

“Actually,” Gaster said, “I’m At The Barrier. Meet Me Here?”

Alphys paused for a moment, her attention briefly derailed by Gaster’s location, but didn’t let that slow her down has she hopped out of bed and flipped the nearest light switch. “B-be there in ten,” Alphys said, grabbing a labcoat to throw over her pajamas as she hurried out the door.

Hotland was quiet in the early morning, resounding with the distant boil of the magma vats that provided the cavern with its only source of light. The phosphorescent gems, which shone like stars in other parts of the Underground, were obscured by the steam and ever present glow of Hotland; even so, it was clear that it was nighttime. Alphys was the only soul walking the earthen streets.

Now that she had the time to think, Alphys wondered about the peculiarity of Gaster’s call. It wasn’t the first time he’d woke her at such an hour, having lost track of time, but this was the first he’d brought up the barrier. And as exciting as any development in that department was, Alphys couldn’t help but wonder why it couldn’t have waited until morning.

It had been two weeks since Gaster had begun shadowing Alphys. Technically, he was working as a “consultant,” but in practice he was learning the ins and outs of the laboratory and all her most recent experiments. Alphys was a little intimidated by how fast he caught onto things. Already he had refined his magic constructs into practical hand shapes, read every text on magic theory the Underground had to offer, and surpassed all of Alphys’ brightest students. Gaster absorbed magical knowledge like a sponge and applied concepts as fluidly as a well-oiled machine—and he showed no signs of slowing.

Alphys had originally planned on offering him an assistantship if he expressed interest in becoming an official member of the royal lab, but at the rate things were going Gaster would soon be just as adept at magical research as she—if not moreso. Alphys couldn’t decide if she found his intellect impressive or frightening. Perhaps it was both.

While an assistantship would be beneath him, she also had her reservations about recommending him for a higher position, such as a lab head or (godforbid) a partner. The most obvious reason for this was that she’d only known him for less than two months. No matter how talented he was, she wasn’t sure if she should trust him to be in a position of authority. Granted, he appeared to consider her a friend and treated her work with respect, but Alphys couldn’t get over all the secrets.

That was hypocritical, Alphys knew, but that didn’t stop it from bothering her.

It wasn’t so much lies as it was half-truths and strategic omissions. Gaster had come from a world without magic and souls (an idea Alphys was still trying to come to terms with) and had undergone a drastic change in the process. But what, exactly, he had been like before was a topic Gaster avoided, and any time Alphys brought it up he managed to deflect and change the subject. He was eager to learn more about her world, but careful when revealing any details about his own. Excited to discuss their similarities, but loath to explore their differences. Alphys didn’t understand why he was so desperate to avoid the topic, and it made her nervous. She had her suspicions, but… they just seemed too outlandish to consider.

Then, of course, there was the nature of his magic. The bone constructs were conventional enough (even with the absurd amount of precision it took to operate them as skeletal hands,) but his magic stores were astronomical. The sudden dips in his magic—and subsequent bleeding from his reopened wounds—happened less frequently now, but Alphys suspected Gaster knew more about those episodes than he was letting on. Possibly, it was an adverse side-effect of transitioning between worlds. If that were the case, then Gaster was maybe playing down the injury out of some sort of misplaced stubbornness and pride. Alternately, the magic was performing something so strenuous that it bit into his health each time it was activated. Alphys couldn’t even begin to imagine what purpose it might serve if that were the case—and Gaster certainly wouldn’t be the one to enlighten her.

Alphys wished he would just tell her what was going on. She wished he would just trust her.

It was a long and quiet elevator ride up to the barrier. Alphys slipped her hand into her coat pocket to rest against her phone. Undyne was only a call away. Undoubtedly, she would put a stop to this night’s processions if she found out, which was why Alphys hadn’t yet called. Though the Captain still kept a wary eye on Gaster, she had backed off in recent weeks, satisfying her suspicions by talking to Alphys at the end of each day rather than pestering the scientists as they worked, as Undyne had been doing until Alphys asked her to stop. It appeared she was reluctantly coming around to the idea that her initial distrust in Gaster was unfounded. All of that progress would surely be undone the moment Undyne learned about a private, midnight jaunt to the barrier. Better to ask for forgiveness than permission, in Undyne’s case.

Though if Alphys ended up regretting this, Undyne’s hubris would be the least of her concerns.

The mechanical hum whispered out as the elevator slowed to a stop. Alphys left her phone in her pocket, worrying her hands as the door opened. The floor was dark and quiet, and a glow of purple shone faintly from down the hall. Alphys carefully stepped out.

“Doctor Alphys?” Gaster called at the sound of her approach.

“Um, yeah,” Alphys said, padding down the corridor. “It’s me.”

Gaster had his hands full with, well, hands. Alphys’ gaze was drawn to the hundreds of pairs of constructs that illuminated the hallway, organizing themselves into a monster-sized shell that hovered in the air. It was unclear what Gaster was trying to accomplish with the structure, and the spot on the wall that reflected its light soon shifted her attention to the barrier. The purple glow rippled over its surface, sinking and resurfacing in the silver expanse. The barrier shifted in a way that made it impossible to focus on, seeming to paradoxically lack volume but project depth. A tesseract came to Alphys’ mind; like trying to view a four dimensional construct in three dimensions, some forms simply weren't compatible with her perception. Perhaps the view _did_ have to do with other dimensional physics. Gaster was from another dimension, after all. Maybe the barrier was not so strange as it seemed.

“Alphys?” Gaster prompted. The scientist jumped, her attention snapping back to Gaster. “I Know That Look—You’re Thinking Of Something.”

“O-oh, um, sorry,” Alphys said, wringing her hands. “Just thinking about the n-nature of the barrier. It’s, um, a bit like you, isn’t it? Something from another dimension? I was wondering if it gave you s-some kind of insight.”

“Hm.” Gaster turned to face the barrier. “Yes, I Suppose I _Have_ Had Some Insight. You Will Be Pleased To Hear That I Believe We Can Pass Through The Barrier.”

 _“What?”_ Alphys rounded on Gaster, who was still gazing at the barrier thoughtfully. “When? How? I d-don’t understand—”

“At Least, I’m Ninety Percent Sure We Can Make It Through,” Gaster amended. “Working Around Its Conditions Is A Bit Tricky.”

“A bit— a b- _bit tricky?”_ Alphys stammered. “Gaster, no one’s b-been able to figure out h-how to break the barrier f-for centuries! Even I f-failed to find a workaround.”

“Not Break It,” Gaster corrected. “It Would Take An Unfathomable Store Of Energy To Unmake This Spell. Seven Human Souls, Was It? I Think I Can Believe That, From The Observations I’ve Made Here. No,” Gaster said, raising a hand. Another dozen of his constructs appeared, joining the others as they interlocked into the structure that was taking shape. The layer of joined hands had formed one large, curved half-shell, and were well on their way to completing a second. “No, We Can’t Break It. But It Takes Much Less Energy To Pass Through It.”

Alphys felt a chill. “A monster and h-human soul.”

“Precisely,” Gaster said.

“Y-you think there’s a way to g-get around that?” Alphys asked.

Gaster didn’t answer, but looked away from the barrier to meet Alphys gaze. The shell constructs continued to build themselves in their periphery. Alphys squirmed under Gaster’s intense look.

“The Most Difficult Aspect To Circumvent,” Gaster said, deflecting Alphys’ question, “Was Figuring Out How To Disguise Two Souls As One Entity. Traditionally, As I’m Told, Only A Monster Who Has Absorbed A Human Soul—Or Vice Versa—Can Pass Through The Barrier. However, I Believe The Absorption Step Is Not Necessary. So Long As The Power Of Both Souls Work In Tandem With The Same Intent, They Should Still Be Able To Pass Through. That Is The Purpose Of This Shell,” Gaster said, gesturing towards the constructs. “Two Passengers Hidden Within Should Be Indistinguishable From A Single Entity That’s Absorbed An Extra Soul.”

Alphys frowned, tapping her claws together. “M-maybe. It’s an interesting theory. B-but that operates under the assumption you c-could find a human and monster willing to work together. It w-wouldn’t work with Asgore’s human souls,” she said, growing tense as she suspected where Gaster was going with this. “A-and, um, I’ve already told you th-that absorbing them isn’t an option…”

“Of Course,” Gaster assured her. “What The King Does With The Human Souls Is Not Of My Concern—And As I Said, It Is Not My Intention That Anyone Should Use Them.”

Alphys slumped will relief. She still hadn’t shown Gaster where the human souls were located—even Undyne wasn’t privy to that knowledge—and wouldn’t have known how to turn him down if he’d asked. Asgore had trusted that secret to Alphys only when she’d become a Royal Scientist. There were some monsters—not many, but some—that would use the souls to leave the Underground, given the chance. If Gaster fell into that category then he had a very good poker face, but Alphys couldn’t afford to take the chance. Not if it meant betraying Asgore’s trust or risking the future of the Underground.

And yet…

“But… if you don’t plan on using any of the human souls,” Alphys said, her frown returning, “then how do you plan to go through the barrier?”

“With _You,”_ Gaster said. “Just Us Two—To Start, At Least. It Will Work.”

Alphys was already shaking her head. “B-but that’s just two monster souls. I don’t understand how… how you could think… that… you...” Alphys faltered as a cold chill washed through her. The explanation—a niggling hunch she’d always suspected but never wanted to believe—came to her, unbidden and all at once. It made complete sense, was embarrassingly obvious, and shot her through with sickening dread. She should have seen in—Undyne had even suspected as much—but it had been too unthinkable for either to take seriously. Alphys swallowed down a bout of panic.

“It w-wouldn’t work,” she said, regretting the action even as she voiced the thoughts aloud, “unless one of our souls were human.”

Gaster’s expression betrayed no emotion, and Alphys braced herself for the outburst. She could have dealt with vehement denial. She could have dealt with laughter and the admission that it was all a very bad joke. She could have dealt with an objection or some kind of reaction— _any_ kind of reaction—but the silence, as it persisted and stretched, was much worse.

Alphys edged a step back. “You _are_ , aren’t you? Or, you were.” His body had been stripped to form the magic of his soul—a soul magnitudes more powerful than a monster’s had any right to be. Of course he hadn’t know anything about magic. Of course he’d been so disoriented upon waking up. Monsters didn’t even exist where he came from, did they?

Her throat tightened, and her next words came out as a whisper. “Oh... oh god.” She fumbled for her phone.

“Alphys.” Gaster’s voice, level and unaffected, made her jump. “What Are You Doing?”

“C-calling Undyne,” Alphys squeaked, flipping the device open. Would he try to stop her? Try to take it from her? He was so much more powerful than her—even if she had trained in combative magic, it would be no fight. She took another step back, her hands shaking too hard to dial the right buttons.

Gaster sighed. “That Would Not Be Wise.”

“W-why?” Alphys challenged. She couldn’t keep the tremble out of her voice. “B-because she wouldn’t believe me, or b-because she’d learn the truth?”

“I Suspect Undyne Would Believe Whatever You Decided To Tell Her,” Gaster said. He wasn’t denying anything, but acting strangely calm. “However I Don’t Think Calling Her Now Would Be A Good Idea.”

Was that a threat? No. “Because you don’t want to be discovered,” Alphys guessed, gripping her phone tightly. “Because then… then...”

Because then Undyne would try to kill him. The king would demand his soul. And if they failed to defeat him—or, Alphys suspected, _when_ they failed to defeat him—countless other monsters would have fallen in his stead. It would not be like the times the human children had fallen into the Underground. Gaster was a fully grown, fully realized mage. There was no way a confrontation with him would end well.

And Gaster was trying to spare them from that.

What was more, he was trying to help them.

Where was the justice in that?

Alphys dropped her arms to her sides and her phone clattered to the ground as her conviction left her with the swiftness of an exhale forced out by a blow to the gut. Alphys sniffed, staring down at the device where it had fallen.

“Alphys.”

Gaster raised his hand and Alphys instinctively jumped back, only to realize after that the gesture hadn’t been to call forth a magical attack. Gaster’s face furrowed in disappointment, though he kept his hand extended as a benign offering.

“I’m Not Going To Hurt You.”

“Sorry,” Alphys blurted automatically. “I know. I mean, I d-don’t _think_ you will, but... I don’t know _what_ t-to think.”

“I Want You To Trust Me,” Gaster said. “Though Perhaps I’ve Ruined The Opportunity For That.”

He was right. How could she trust him knowing what she knew? Given what he _was_. They were supposed to be enemies. Even if he was from another world and didn’t share her history, her King had still declared war on his kind. Alphys hadn’t enjoyed working with the human souls—hadn’t enjoyed watching Undyne capture and slay those children—but she had grown used to it, insulating herself in the mantra that it was all for the greater good.

Now she didn’t have the luxury of detachment. The fact that Gaster had lied to her hurt, even if he’d done it out of self preservation. Could she trust a human?

Could _he_ trust _her?_

Alphys shook her head, though even she wasn’t sure what she was shaking it at. “Why are you doing this?”

“This?” Gaster raised an eyebrow. “Doing What?”

“T-trying to help with the barrier,” Alphys said, nodding in its direction. “W-why would you want to do anything for us? Knowing… knowing… the h-human souls…”

Gaster let his hand drop, frowning as he glanced towards the barrier. The light from his constructs were reflected in the silvery surface, cast back on Gaster in a strange, watery glow. It made the shadows in his bones seem deeper, and the cracks in his skull more grievous. In the artificial twilight, it looked like it wouldn’t take much for him to break apart.

“I Can’t Say I Agree With Or Approve Of Your Methods,” Gaster finally spoke, “But That Is Irrelevant To My Motives. No One Deserves To Be Trapped In Such A Prison. You Thought I Might Be Able To Help, So I Felt I Should Try. Besides,” Gaster glanced back towards Alphys, a hesitant smile tugging at his mouth. “I Just Can’t Say No To A Challenge.”

“Heh.” Alphys tried and failed to share the smile. “J-just because it’s a challenge?”

“By And Large,” Gaster admitted, his smile growing more smug. This time, Alphys did smile.

“I g-guess that doesn’t surprise me,” she said.

“I Hope That Doesn’t Mean I’m Growing Predictable.”

Alphys’ smile became strained. “I, um, w-wouldn’t say that.”

“Ah.” Gaster sobered as well, and their moment of levity passed. “That’s Fair.”

Gaster turned to look at his magic constructs, clasping his hands behind his back. The two half shells had finished forming and were hanging before the barrier, each glowing a soft purple. At a silent instruction from Gaster, the shells drifted down to rest on the ground before him. Each stood a head taller than Gaster himself.

“I Don’t Like Misleading You About Things,” Gaster spoke over his shoulder. “It’s Been An Unfortunate Necessity To Date, But I Hope To Be More Honest WIth You Henceforth. I Do Enjoy Your Company, And Would Like To Consider You A… A _Valued Colleague_ ,” Gaster said haltingly. “If We Make It Through—If We Are Able To Pass Through The Barrier And Free The Underground—I Will Answer Any Questions You Have For Me. I Think I Owe You That Much.”

Alphys squeezed her hands together until her nails bit into her palms. “Y-you don’t owe me anything.” She bowed her head, feeling sick. “That’s n-not fair. I w-wanted to call Undyne, and you’re j-just trying to help.”

“Well, I Do Appreciate That You’ve Decided Not To Call Her,” Gaster said, turning back to face Alphys. “A Change Of Heart?”

Alphys shrugged, staring at her hands. “It w-wouldn’t be right.”

Gaster tilted his head. “How... Compassionate Of You. But If You’re Really So Concerned About Fairness, Then Perhaps We Can Call It Even When You Help Me Try To Find A Way Home.”

“O-of course,” Alphys said, risking a look up. Gaster’s expression was unreadable. Was he perplexed? Amused? Grateful or relieved? The conversation had already been a rollercoaster of emotions, and she wasn’t sure which of those she was feeling herself. “I w-would have tried to help you anyway.”

“Does This Mean You’re Willing To Try?” Gaster said, guesting towards the barrier. “If We Succeed…”

Alphys nodded shortly. “I know. I know w-what’s at stake.”

“Well, Then?” Gaster said, extending his hand once more.

Alphys took in a breath, and let it out. She looked to the barrier, looming silently over their conversation, and Gaster’s shell constructs, hinged open like the mouth of a flytrap. Between them Gaster painted a macabre visage, a skeleton beckoning her towards an uncertain fate.

A skeleton, it was hard to miss, that wore glasses and an ill-fitted lab coat. A skeleton that consumed books like candy and struggled with pleasantries more than foreign languages. A skeleton that, despite his genius, had managed to get his hand stuck in a solenoid while assisting with Core maintenance just last week. (Alphys had never seen anyone so embarrassed in her life.) A skeleton that took Alphys’ work seriously, and had provided the most engaging scientific conversations she’d had in years.

“Okay,” Alphys said, taking a step forward. When she accepted Gaster’s hand, her own was no longer shaking. Alphys looked up at her friend. “Let’s save the Underground.”

Gaster face split into a grin as he wrapped his fingers around hers. “Let’s.”

 

 

 

**Notes for the Chapter:**

> And then everything went exactly as planned and everyone lived happily ever after.
> 
> ...Right?


	9. A Terrible Depth

**Summary for the Chapter:**

> “There are no beautiful surfaces without a terrible depth.”

The shell halves closed around them without a sound, and the seam vanished as the construct’s fingers laced themselves together. With his free hand Gaster touched the inner surface of the shell, and a shimmer passed through the magic. The bone pattern rippled away, leaving a smooth, translucent surface in its wake. Some of Alphys’ claustrophobia eased as the room beyond the shell became visible once more—even so, she had yet to let go of Gaster’s hand, and he seemed equally intent on maintaining the grip. Perhaps a physical connection was necessary for the magic to work.

“Right,” Gaster said, moving their bubble before the barrier. “Remember, To Trick The Spell We Need To Act With The Same Intent: _‘Pass Through The Barrier.’_ That Shouldn’t Be Too Hard To Keep In Mind.”

“R-right,” Alphys said.

“Good.”

There were several seconds of silence.

“...Gaster?” Alphys prompted.

“Hm?” Gaster said with a small start.

“Um. Are you ready?”

“Yes,” Gaster said. “Yes, Of Course. Are You?”

“N-no,” Alphys admitted. “I mean, it’s hard t-to believe this is actually happening after all this time. It almost d-doesn’t seem real. A-and I’m a little nervous.” She looked up at Gaster. “It’s okay to be nervous.”

“That’s Perfectly Fine, Alphys,” Gaster agreed, clearly missing the intended consolation. Or ignoring it. “But You Shouldn’t Worry Too Much. After All, The Worst Case Scenario Is That The Shell Fails, We’re Recognized As Two Distinct Souls, And We’re Kicked Back Out Into The Underground. We Can Always Try Again.”

“Okay,” Alphys said, suspecting the pep talk hadn’t been for her benefit. “Then, good luck?” she suggested.

“Good Luck,” Gaster agreed. Raising his hand, the shell lifted from the ground and drifted into the barrier.

Ignoring the magic bubble as if it were as insubstantial as mist, the surface of the barrier washed through the shell and over Alphys and Gaster. Alphys took in a startled breath just before the silver light overtook her, though she felt nothing as it obscured first her body and then her sight. She let out a nervous breath and drew in another, feeling her chest expand and contract without the sensation of air passing through her lungs. The realization caused her to gasp—a sound that never made it to her ears. Alphys blinked rapidly against the blinding light, beginning to panic as each of her senses failed her. It was only when she tensed, instincts screaming at her to turn and flee, that she felt something solid in her grasp. Alphys squeezed it tightly, and Gaster’s hand squeezed back.

Using the sensation to ground herself, Alphys turned her attention to the task at hand. _Pass through the barrier,_ she reminded herself. She couldn’t risk becoming distracted now. Her panic had been brief, but could have jeopardized their mission. She and Gaster needed to act as one or everything could fall apart; it was her responsibility to stay focussed. _Pass through the barrier,_ she willed. _Pass through the barrier._

It was difficult to concentrate without any sense of self. More than once Alphys had to tighten her grip on Gaster just to remind herself that something else was there. She had no idea how long this was supposed to last, but as the seconds ticked on, remaining calm became an increasingly daunting task. Surely the process shouldn’t take more than a minute? How long was the passage supposed to be?

 _Pass through the barrier._ Her will became desperate. _Pass through!_

The air grew heavy. Alphys hadn’t been able to sense anything before, but now there was a pressure all about her. It was a weight that pressed on her mind. A thickness that slid through her soul. Alphys went to squeeze Gaster’s hand once more, but found nothing there.

She couldn't find anything _anywhere_.

Alphys’ composure slipped. She tried to reach out, but was unable to move her body. There was no way to run, or cry, or scream. In fact, she couldn’t sense her body at all. All that existed was her mind, the pressure of the barrier, and a crushing sense of helplessness.

Alphys lashed out with her will. _Pass through,_ she thought. _Go back. Help. Stop. Let us go!_ This had been a mistake. A terrible, fatal mistake. Trying to trick the barrier—what had she been _thinking?_ She never should have let Gaster talk her into this. It was absurd. What did they know of this magic? Of a curse, cast centuries ago and preserved for just as long. How arrogant they had been. How naive.

 _Gaster,_ Alphys called out. _Anyone?_

At the thought, an entity appeared. Alphys recoiled, not expecting her call to be answered. The other being didn’t move, and as Alphys concentrated she realized she couldn’t sense _anything_ from it apart from its mere presence. Hesitantly, Alphys tried to reach out, but there was a vast space between them. Pushing a little harder, Alphys felt the barest hint of… _something_. An identity. A soul.

_Gaster?_

The other presence radiated an awareness, and she felt its attention fall over her. It _was_ Gaster, she realized, in the most abstract of ways. Encouraged, she tried to reach out to him again; her will, however, didn’t seem to mean much in this place, and Gaster remained untouchable. Communication was just as much beyond her as movement or sight. After trying and failing to interact in other ways (intent, magic, will,) she gave up, and felt Gaster’s attention leave her. Perhaps he had been trying the same, and his attempts to reach her had been just as futile. It was enough, however, to know she wasn’t alone. Curious and exhausted, Alphys let her focus drift, searching for whatever it was that had drawn Gaster’s scrutiny. It wasn’t difficult to find.

There was something far, far beneath her. It was a light, though not the kind she could see. A speck of brightness against white. A warmth against heat. She peered harder, looked more intently, and as her attention narrowed in, the irregularity zoomed up to meet her.

It wasn’t light or warmth, Alphys realized, but magic. A consciousness in the miasma. The entity was pushing through its surroundings, oblivious to the webs of spells that snagged at its surface and tremored their findings back through a magical network. Some strands broke while others trailed after their mark. The spell complex had not yet reacted to the presence of the foreign magic; it was still gathering information.

Inside the entity were two souls. Both displayed a delicate balance of traits, though one shone largely with justice while the other was dominated by perseverance. Alphys recognized the first immediately, and it was only after a small delay that it became obvious who the second belonged to as well. A mental vertigo accompanied the realization that, somehow, Alphys and Gaster were looking down on themselves as they attempted to pass through the barrier.

The tangle of spells continued to feel them out. Alphys could detect impressions of the information the barrier was gathering, sense fleeting synapses of magic as they pulsed back through the network. For the moment, Gaster’s shell appeared to be working; the barrier, as of yet, had deduced little more than the presence of an entity that was willing itself to cross. (And Alphys _was_ willing it; a part of herself, down in the shell, was still repeating the mantra to ‘ _pass through, pass through,’_ even as the rest of herself viewed the scene as an impartial spectator.)

It was as she was watching the spell’s logic unfold that Alphys realized almost no time had passed at all. In fact, judging by their progress, they were still within the first second of entering the barrier.

At some point after she had entered—perhaps even the moment she had made contact—Alphys’ perspective had shifted to match that of the barrier. The spell, roused from timeless standby, had begun to execute its routine, and Alphys was experiencing it in real time.

Much as a computer could execute a thousand lines of code in the blink of an eye, Alphys witnessed the barrier weave and implement a thousand spells in a similar manner. All the time that had passed before now had been spent setting up the initial conditions, performing self checks, and reading the inputs. And now, finally—after some odd milliseconds—it was time for the spell to perform its intended purpose.

 _One entity,_ Alphys felt it conclude. _Pass._

_Two souls. Pass._

_At least one monster soul. Pass._

_No human souls._ The spell paused.

What? Alphys wasn’t sure she’d interpreted that correctly. No human souls? That couldn’t be right. The spell stuttered and scanned the entity once more.

 _Two monster souls,_ the barrier confirmed. _No human souls. Fail._

The aftermath unfolded slowly, and in an instant.

Alphys’ full consciousness snapped back to her body. She had enough time to register the pressure of Gaster’s hand back in hers before she felt the barrier react, fierce and repulsive.

If it had been a physical sensation, it would have been pain. Instead the rejection swept through her with startling precision, ripping apart Gaster’s shell in its urgency to expel them. Alphys crashed to the floor, rolling several times before she had the presence of mind to throw out an arm and skid to a halt. Her vision spun from the tumble, inhibited further by the loss of her glasses somewhere along the way. The stone floor was cold beneath her, yet it seemed a tempting place to rest as she caught her breath and nursed her bruises. Where was she? Had the barrier—

“ _No!”_

A flash of purple burned across her vision.

“No, You’re _Wrong!”_

Another spark of light flew across the room. Alphys rubbed at her eyes, as if she could massage away her blurred sight, and propped herself up on an elbow. A furious scream caused Alphys to cower back, and a crackling wave of magic permeated the room.

“Broken!” A purple lance of light manifested, flying through the air to vanish silently into a wall. “Decrepit!” Another array of lights formed and shot forward. _“Wrong!”_ The room flashed with purple light as the air filled with the constructs—bones, Alphys could finally make out—that launched themselves in an endless volley towards the barrier. Alphys hunched down, trying to make herself a smaller target as the magic haphazardly ripped through the room.

The attack lasted for almost ten minutes. It was the most chaotic, exorbitant display of magic Aphys had ever witnessed. Even the sparring sessions she’d watched between Undyne and Asgore had never approached such bottomless wells of magic. A similar act, performed by any other monster, would surely have drained their reserves and killed them. In fact, that was still a possible fate for Gaster, and one that was growing increasingly likely by the second.

Alphys could feel the magic weaken as the pointless onslaught progressed. By the time only a handful of bones were forming and launching at once, she could hear Gaster panting over the ambient buzz of magic. Inevitably, the violet lights began to stutter, and the room finally went dark as the last of them flickered out. Gaster clattered to the ground a moment later as his dwindling magic reserves failed to support him. Waiting another moment for fear he’d find some renewed pool of strength, Alphys carefully pushed herself up to her knees.

“...Gaster?” she whispered. She could still hear him breathing heavily a dozen paces away, though he made no effort to reply. The only light source in the room now came from the barrier, providing a faint, silvery glow that cast about the room in watery shimmer. Even so, it wasn’t enough to make out her surroundings, so Alphys carefully leaned forward and began to pat at the ground around her. A glint of light reflected off something nearby; gingerly, Alphys felt for the glasses, accidentally bumping into them and sending them skidding a few inches away before she picked them up. The shape of the lenses told her they weren’t hers, but she fitted the glasses on regardless. Alphys squinted, her eyes watering as the scene sharpened into a warped depth. They wasn’t perfect, but it was enough for her to find her own pair only a few feet away. Swapping Gaster’s out for hers, she clutched the extra set of spectacles to her chest as she finally turned her attention to the real problem.

“Gaster?” she called again, a little louder this time. She could faintly make out his silhouette, sitting not far from the barrier. One leg was splayed out in front of him while the other was bent, and he was leaning back on both arms, still catching his breath. Alphys stood there for a long time—too long—before her embarrassment became too much to bear, and she lurch forward into a halting gait.

“U-u-um,” Alphys stammered, forcing herself a few steps closer. She stopped within arm’s reach of Gaster, but he had yet to acknowledge her. Alphys stuck out her hand. “You, um, dropped these.”

Gaster stirred. Turning his head, he stared towards Alphys’ outstretched hand. His eye-lights flickered briefly over his glasses, up to Alphys’ face, then back towards the barrier. The action was automatic, a response to a stimulus, and nothing more. His gaze was dead. When his head turned back the light glinted off of his skull, streaked with ethereal tears and blood. Alphys gasped.

“Y-you’re bleeding again,” she said. “You sh-shouldn’t have used so much magic. I n-need to get you checked out, m-make sure you didn’t—”

“It Should Have Worked,” Gaster said. Alphys stammered for a moment before trailing off. His voice was soft, hard to make out even in the silent cavern. “I Was So Sure It Would Work.”

Alphys quavered. “W-w-well, like you said, um, we can always… try again?”

“It Can’t Be Right,” Gaster said, as if Alphys hadn’t spoken. “It Can’t Be.”

Alphys spared the barrier a glance. It wasn’t hard to guess what he was talking about.

“It’s Not Fair,” Gaster said. “I’ve Lost Too Much. I Can’t Lose This, Too.”

Alphys didn’t know what to say to that. “M-maybe it was wrong,” Alphys suggested. “M-maybe—”

“ _Two Monster Souls,_ ” Gaster croaked, finally looking at Alphys rather than through her. “You Could Understand It, Too, Couldn’t You? When We Were In There? Could You Feel How It Picked Our Very Essence Apart? Exposed Our Deepest Selves?”

Alphys shrunk in on herself. “I d-don’t know,” she admitted, blinking rapidly as she tried to decipher his outburst. “I c-could see us how the b-barrier saw us. I c-could sense what it d-detected, but—”

“It Was More Than That,” Gaster said, and as quickly as his temper had flared it guttered out. His voice broke when he spoke again. “It Was So Much More Intimate. It _Knew._ It Could See Everything—I’d Just Refused To Consider It. It Was Unthinkable— _God,_ It Still Is. It’s Too Much, It’s Just Too Much...” Gaster passed a hand over his face, smearing blood and faint, violet streaks of magic over the bone.

This time, Alphys remained silent. What was there to say? She still wasn’t sure she understood or believed everything that had happened. To learn one moment that Gaster was not the monster he’d pretended to be—and then find out the next that even he hadn’t understood the full extent of the changes he’d undergone... what did that make him? A man, a monster, neither, or something between?

One thing was clear: the barrier had not detected a human soul.

Alphys jumped when Gaster’s hand fell over hers. Carefully, he took his glasses from her grasp, though he didn’t move to place them back on his face. Instead he brought his knees up to his chest and wrapped his arms around his legs, resting his head on his forearms.

“My Family,” Gaster breathed, “My Partners And Colleagues. My Home. My Body. I Suppose My Degrees Mean Nothing Here As Well. I’ve Forfeit So Much, But With This… I Have Nothing Left To Lose.”

Alphys reached out, hesitated, then pulled back. “Surely… n-not nothing?”

Gaster tilted his head to the side to peer at her with one eye. The cracks in his skull—especially the gash above his right eye and below his left—were still oozing blood; his body didn’t have enough magic to staunch the flow. If the wounds pained him, he didn’t show it. His gaze was far away, empty and broken. Magic still clung to the rim of his eye sockets, though there wasn’t enough left for any new drops to fall.

“Please Go,” Gaster said.

Alphys obediently took a step back.

“Y-you’re still hurt,” Alphys tried again. “I-if you don’t get those fixed they’ll scar. You n-need a healer or—”

“Dr. Alphys,” Gaster cut her off. “What I _Need_ Is To Be Left Alone.”

Alphys winced, taking another step back. “O-okay.” She could only offer him help; whether or not he’d accept it was out of her hands.

Gaster closed his eyes, yet Alphys lingered. What could she do? Calling for help would lead to questions she didn’t want to answer. Her own magic wouldn’t be useful here either—not that Gaster would let her try to help, anyway.

“I… I’m sorry,” Alphys said. When Gaster didn’t respond, she decided it was time to leave. Crossing the room with quiet shuffling of her feet and clothes, Alphys stopped at the elevator to look back; Gaster still sat before the barrier, head bowed. In his situation, what would she do?

Panic, probably. In fact, the way he’d handled everything was far better than Alphys would have managed. She didn’t suppose telling him that would make him feel better.

Yellow light spilled into the hall as the elevator door opened.

“If you need anything,” Alphys said, trying one last time. “Just let me know. I’m, um, a real good l-listener. If you ever want to talk.” The elevator doors began to close and Alphys stopped it with a hand. She waited for Gaster to indicate that he’d heard, or display any kind of reaction, but the monster remained silent. With a sigh, Alphys turned away. The elevator hummed as it descended, carrying her back into the depths of the Underground.

 

 

 

**Notes for the Chapter:**

> So it goes. 
> 
> \---
> 
> I have a strong suspicion the next chapter is going to be very long. Should be the penultimate chapter, if I planned this right. I might actually write both next chapter and the final chapter before I post either, so expect it to take a longer than usual to come out. 
> 
> Thanks for reading.


	10. Best Laid Plans

**Summary for the Chapter:**

> Chapter aptly named, as it caused me to changed the total chapter count for this story. I was about 6k words in when I realized I still had at least 1-2k to go... so I made the decisions to split it in half. Silver lining: the next chapter is already halfway done, so it shouldn't be long before it's up. 
> 
> We're approaching the end of this tale.

Gaster drowned himself in his work. It wasn’t difficult to keep busy; there was always something to be working on.  

His background in engineering and energy storage proved invaluable for improving the Core’s design. The framework for an extension to the Hotland laboratories was in the process of being installed, strung above the open magma planes between the main lab and the Core like a lattice of metal spiderwebs. (In fact, the spiders of the Underground had been useful consultants on the design.) The labs’ placement wasn’t ideal, in Gaster’s opinion, but the nature of Hotland’s terrain made solid land a rare commodity to build on. The suspended labs, like the suspended paths and walkways, were necessary evils.

In less than three years, the Core had begun to produce peak efficiencies, most of the Underground had become supplied with power, and the scientific industry had boomed as a result. Alphys had become overwhelmed with applications to work in the labs—and had been all too eager to let Gaster take the vetting process off her hands. There had been no official announcement or promotion; Gaster had gradually taken on more responsibilities until one day he was doing as much to run the lab as Alphys—and the next day he was doing more. They were both Royal Scientists, technically, but Gaster suspected Alphys was relieved to have someone else step into the leadership position.

And probably, he mused, a subconscious part of her was still too wary of him to challenge his authority.

“Ugh, _boring_.”

Gaster tightened the bolt another quarter turn, ignoring the complaint. Leaning back to work a kink out of his neck, he tested the brace’s hold. It seemed study enough; the animal-like skull entombed in the scaffolding was secured snuggly in place. Only another day or so until he’d be ready to try out the interface.

“You haven’t said _anything_ ,” Flowey continued when Gaster didn’t respond. “Usually you’re at least talking to yourself like some kind of weirdo.”

“Working Through Problems Aloud Often Brings Clarity,” Gaster said. “However, This Work Is Rather Simplistic. My Thoughts Were Elsewhere.”

“What’s it even supposed to do?” Flowey asked, popping up beneath the skull to get a better look. The device was a meter long and half as tall, machined out of calcite and inert donor magic.

“If It Works,” Gaster said, “It Will Act As A Proof Of Concept For Magic-Machine Hybrids. We Already Implement Similar Technology In The Core—Devices That Operate WIth Magical Energy—But This Will Be The First To Be Built Of Both, Connected Directly To The User’s—”

“Yeah but what does it _do_?” Flowey interrupted. Gaster’s mouth quirked in irritation.

“It Should Channel And Convert The User’s Magic Into Concentrated Energy, Which Can Then Be Directed And Expelled At Will,” Gaster said. Flowey stared at him. The doctor sighed. “It’s A Laser Cannon,” Gaster said.

“Woah, neat!” the flower exclaimed. “Could you make me one?”

“It Will Be Quite Draining,” Gaster said. “I Don’t Think You Have The Magical Reserves Necessary To Operate One—Even If I Scaled It Down.” Not to mention Gaster wasn’t comfortable with the idea of giving Flowey a weapon. As useful as he had been with helping Gaster to figure out his temporal powers, the flower was quite clearly some vein of sociopath.

“Oh well,” Flowey said, not obviously disappointed. “I’m more interested to see what you’re going to use it on.”

“I Don’t Plan On Using It _On_ Anything,” Gaster said. “As I Mentioned Before, It Is Merely A Proof Of Concept. The Simplest Application Of Hybrid—”

Flowey interrupted with a rude noise intended to replicate a bodily function. “Booooring. What’s the point of having a weapon if you’re not going to use it?”

Gaster frowned. “Don’t You Have Better Things To Do?” The answer, he already knew, was ‘no.’ The flower seemed to take particular delight in bothering him. At this point, Gaster wasn’t sure why he still put up with him; the balance of pros and cons that Flowey’s company provided was tenuous. It had been over a year since the flower had had any useful information to provide on Gaster’s powers. Still, Flowey’s history proved to be an enigma—and Gaster hated the idea of not figuring it out.

“So what else are you working on?” the flower said, switching tracks. “You’ve got so many projects going on at once.” Flowey swung his head to looking around the lab in an exaggerated gesture. He wasn’t wrong; Gaster’s workshop had accumulated a wealth of devices and tools, both magical and mechanical in nature. He was rather proud of how much he’d accomplished in such short time, truth be told, and would normally take the opportunity to boast a bit about his most recent obsession. Gaster doubted, however, the change in topic had been made without some duplicitous intent. He waited for whatever Flowey was planning to say next.

“...How’s the time machine coming?”

And there it was. Gaster should have expected as much; it had been too long since Flowey had last reminded him of that particular shame.

“Out,” Gaster ordered, returning to his work. Flowey knew better than to cross that line.

“What?” The flower feigned innocence. “I just thought that if you _really_ wanted to get back home your plans would have matured by now. You _do_ still want to get home, don’t you?”

“Out,” Gaster said again. He wouldn’t stoop to engage Flowey’s provocations.

“Gee, you sure are acting defensive.” The flower’s tone became saccharine, taking on a sardonic edge that Gaster loathed most. Stars, Flowey was testing his patience. “I’m just trying to help you, friend! Maybe give you the push you need to finally get out of this slump. Don’t understand what you’re so broken up over, anyway. I mean…”

“Flowey,” Gaster warned.

“...being some sort of freaky hybrid isn’t such a bad thing—and I should know!”

It stung, even after all this time. Gaster shoved his anger away the moment it started to bubble up, clamping down on the emotions with a practiced effort. Letting out a frustrated sigh, he turned to regard the flower. Gaster might have been more upset by the comment if Flowey hadn’t also let slip something about his own nature.

“What Do You Mean By That?”

Flowey either didn’t realize he’d admitted something, or was pretending like he hadn’t. “You can’t let what you _are_ dictate your actions.” His smile was still sickly sweet. “Can’t let anything get in the way of what you _want._ Don’t you _want_ to go home?”

If Gaster hadn’t known better, he might have thought Flowey actually cared; the reality, of course, was that Flowey wanted his powers back, and they both suspected that would only be possible when Gaster left. Or died. Flowey probably had no preference.

“What Did You Mean By ‘You Should Know?’ What Are You A Hybrid Of?”

“Unless you’re _scared,”_ Flowey said, ignoring the questions. In contrast to his chipper tone, his expression took on a spiteful twist. “Maybe you think they won’t accept you.”

Returning to an Earth without monsters or magic, acceptance would likely be an issue, but it wasn’t what was preventing Gaster from trying to go back.

“Or maybe you’re scared they’ll _attack_ you,” Flowey added. Now he was trying to get a reaction out of Gaster. “Is it the same there? Kill or be killed?”

 _Far more likely to be killed in the return trip,_ Gaster thought grimly. There was no guarantee magic even worked in his universe. Would returning to it return him to his original form? Or would his magic simply scatter as nothing more than an aimless burst of energy? Perhaps if this world’s magic had recognized him as human it might have lent some hope to the theory that he could return, but as things were…

Gaster’s phone began to buzz. A hand construct retrieved it from his workbench, bringing the display up to Gaster’s face.

“Alphys,” Gaster observed, and Flowey let out a disappointed sigh. Saved by the bell, it seemed. Gaster picked up.

“Hello, Doctor,” he said. “You Just Relieved Me From A Rather Trying Conversation.” Flowey stuck his tongue out; the flower avoided Alphys like the plague. He’d still yet to puzzle out the history of those two. “What Can I Do For You?”

“U-um, hi, Gaster,” Alphys mumbled. Something was off about her tone. Her response more subdued than he’d expected. “There’s, um, it’s not something you can d-do for me. But, um, I think y-you should come to the palace.”

Her voice was shaking, and her nervous tick was more pronounced than usual. This wasn’t just a casual call about the Core or her research.

“What’s Wrong?” Gaster said, already standing.

“It’s, um, i-it’s Undyne,” Alphys started, tripped over her words.

“Is She Hurt?” Gaster asked, already mentally running through the category of machines he had at his disposal. Not many were good for healing.

“N-no,” Alphys said, “I mean, yes, a l-little, but that’s not the reason—oh geez, it’s, it’s, it’s a _human_.”

Gaster went still.

“...U-Undyne just retrieved them,” Alphys said when Gaster didn’t immediately respond. “A-another f-fallen child. I, um, I didn’t n-notice right away b-because I wasn’t in my lab, b-but the sensors detected the an-nomalous magic almost r-right away, but, but by the time I got back to the c-console they’d already advanced t-to Waterfall and Undyne had, had…” Alphys paused in her rambling to take a breath. “D-doctor Gaster? A-are you still there?”

“Yes.” His response was automatic.

“O-okay,” Alphys said, sounding even less sure than before. “That’s… Good. Um. Then I th-think you should m-meet me in the palace. Undyne is already on her w-way. T-to Asgore.”

There was a long pause before Gaster remembered to speak. “Alright.” There was an even longer pause before he added, “I’ll Be There Shortly.”

“Okay. Good. S-see you there.” Alphys didn’t hang up. There was a serious of scratchy thumps as Alphys fiddled nervously with her phone. “A-and Gaster?”

“Yes.”

“I, I just w-wanted to say, um… you know… er...” Alphys trailed off, and then a heavy sigh crackled through the phone’s speaker. “I guess… sorry. Nevermind. I’ll s-see you soon.”

The line went dead.

Gaster stared at the ‘Call Ended’ screen for several seconds, his extra sets of hand constructs slowly winking out around the room. Gradually, Gaster reached out for the phone, which fell into his hand as the last set of constructs vanished. Robotically, he turned off the screen and put the phone in his pocket, then simply stood there.

The silence in the lab was interrupted by sudden and uproarious laughter. Gaster didn’t even flinch.

“ _Golly,_ ” Flowey wheezed. “This is going to be _so_ much better than laser cannons!”

 

“Wait.”

The soul was yellow, the color of justice. It had manifested in front of the child’s chest, brought out by the trauma that had been inflicted upon them. Undyne held them by the scruff of their shirt, which didn’t stop the child from trying to stand straight, despite the fact their feet barely scraped the ground. They glared at Gaster, though he could sense their fear as it radiated from their soul. Blood stained their shirt and was crusting over into raw scabs on their cheek and forearms; they had put up quite a fight.

Following the gauntlet up to its owner, Gaster found Undyne was also staring at him. She, too, had sustained injuries in the fight, though her armor appeared to have protected her against much of the human’s attacks. There were a handful of divots in her chestplate, as if someone had taken a hammer to its surface, and a thin cut on her forehead was dusted over, glowing faintly as it stitched itself back together. Undyne’s eyes narrowed, but it was Asgore that spoke.

“Doctor Gaster,” the King spoke. His voice was so deep it resonated in Gaster’s bones. “Is there something you wish to say?”

It was only then he noticed everyone was watching him. Asgore, Undyne, the human, Alphys, even the other guardsmen—all studying him closely. Their reactions ranged from surprised to suspicious, with Alphys hovering somewhere around apprehension. Why were they looking at him?

Ah. Right.

“Wait,” Gaster repeated. He hadn’t realized he’d said it aloud the first time. “This Marks The Sixth Child?”

“Sixth  _human_ ,” Undyne emphasized. Was that a way for her to distance herself? Perhaps she wasn’t as comfortable with her orders as she let on. “What of it?”

“Just Confirming,” Gaster said. More like thinking aloud; he didn’t have time to formulate a plan. “And It’s Been Over A Decade Since The Previous Human Fell, Correct?”

“Eleven years,” the King confirmed. “And nearly fifty years since the human before that. Forgive me, Doctor, but if this isn’t immediately relevant to my duties, then I would prefer to get this over with…”

“It’s Relevant,” Gaster said. Alphys appeared to be growing more nervous by the second. What did she think he would say? “Then, If I Understand Correctly, It’s Impossible To Predict When The Next Human Might Fall,” Gaster said.

“N-not necessarily,” Alphys finally spoke up. “S-since this one and the last h-had a much smaller window between their falls, it m-might be indicative of a human p-population growth. I-if that’s the case, then there m-may be a greater chance the n-next ones will fall soon, too.”

 _Not helping, Alphys,_ Gaster thought. “Still, That’s Speculation,” he said. “If No More Fall, Or If Enough Vanished Children Result In Restricted Access To The Mountain, Then It Could Spell Trouble For Your Plan To Obtain Seven Human Souls.”

“Where are you going with this?” Undyne interrupted. Asgore, though not quite as impatient as his Captain, rumbled a low tone of agreement. Gaster ignored the others and focussed his attention directly on the King. There was only one person in this room he had to convince.

“I Believe It May Be Possible To Break The Barrier With What We Have Now,” Gaster said. “Soul Power Is Regenerative. If We Were Able To Harness The Power Of A Living Human Soul—Drain It, And Wait Until It Naturally Replenished—We Maybe Be Able To Forego Waiting For Another Human To Fall. Trick The Barrier By Using The Power Of One Soul Two Times.”

Undyne made a _tsk_ of obvious skepticism, while Asgore held Gaster’s gaze. Without looking away, he spoke, “Doctor Alphys. You have experience in soul research. What is your opinion on this?”

“W-w-well I’ve never worked with living human souls,” Alphys stuttered. “A-and I’m skeptical we would b-be able to trick the barrier. We’ve failed at s-similar attempts in the past.” To his credit, Gaster didn’t flinch at the remark. “B-but I don’t see a downside in t-trying. It might be w-worth a shot.”

_Thank you, Alphys._

Asgore rumbled thoughtfully, but didn’t comment.

“I Am Not Asking You To Forfeit The Soul,” Gaster pressed. “I’m Just Asking For A Little Time.”

“How much time?” the king asked.

 _Weeks. Months._ “Three Days,” Gaster said. “Then We Can Reconvene And I Can Show You What I’ve Come Up With. Is That Acceptable?”

Undyne made a sound to object, but a gesture from Asgore silenced her. “I suppose I have managed to wait this long,” the king sighed. “Another few days won’t change anything.”

Gaster bowed his head in gratitude. “Thank You, Your Majesty. I Won’t Waste This Opportunity.” Gaster glanced once more at the child; they were still glaring at him, scared and angry.

 _I’m not your enemy,_ Gaster thought as Undyne forced them away. The kid stumbled from the shove, and Gaster turned his back to the sight. _Though you likely won’t believe it from my actions._

Alphys caught up to him only a few paces out of the Throne Room.

“G-Gaster!” she panted, struggling to match his stride. Each of his steps outpaced two of her own, and every so often she dropped a hand down to the floor to help skip forward. “What are y-you _thinking_?”

“I’m Thinking That I Would Prefer To Avoid Bloodshed,” Gaster said.

“I g-get that,” Alphys said. “But what’s your p-plan?”

“Honestly?” Gaster spared her a glance; she was starting to sweat. “I Don’t Have One.”

 _“What?_ ”

“I’m Improvising,” Gaster admitted. “Didn’t Have Much Time To Prepare.”

“B-but,” Alphys said, “But what are you going to d-do when you m-meet with Asgore again in three days?”

“Not Sure,” Gaster said. “Show Him Some Plans, Hopefully. I’ve Got Some Ideas, But I’ll Need Some Time To Flesh Them Out. If He Likes Them, Then I’ll Ask For More Time To Start Work On… Whatever I Figure Out.”

“Th-that doesn’t sound like a very good plan to me,” Alphys said. Gaster didn’t argue the point. “A-and I don’t know if he’ll give you more time—at least n-not as much as you’d need to design and build new technology.”

“Do You Have Any Better Suggestions?” Gaster asked. Alphys hesitated, then shook her head.

“I… I just hope you know w-what you’re doing, Gaster,” she said.

Gaster set his jaw, expression grim. “Me Too.”

 

He didn’t sleep the first night. The moment Gaster returned to his workshop he set about acquiring his tools—ink and compases and large rolls of paper for his drafts. There were more bad ideas than good ones but Gaster wrote each of them down, pursued every option he could conceive, and filled countless pages with each of his ideas, however big or small. Some drafts were simple, hardly legible scratches that bullet-pointed rough concepts, while others detailed intricate designs that spilled over meters of the draft paper, too complex to ever be practical. Gaster had dozens of sets of hands each elaborating on separate ideas, his workshop ablaze with the purple light his constructs cast, working ceaselessly. It stretched Gaster’s ability to multitask, and at one point he was forced to banish a few sets of hands, finding the quality of work suffering from his split attention. He couldn’t afford to lose more, however. He didn’t have the time.

It wasn’t until late morning on the second day that he emerged from his room, blueprints in hand. Gaster wasn’t sure it was the answer he’d wanted—or that the king would accept—but it was all he could come up with in the limited time he had. Even so, there was no guarantee it would work. Despite the time spent working with Alphys, his knowledge of souls and magic was still woefully lacking when compared to a lifetime of experience with such things. Hopefully, Alphys could fill in whatever gaps his plans had.

He arrived at her door in the same clothes he’d been in when they’d previously parted. That in itself wasn’t out of the ordinary (for either of the monsters,) but judging by Alphys face he must have looked as worn as he felt.

“Gaster!” she exclaimed. “Have y-you slept at all? Eaten anything?”

“I Have A Plan, Alphys,” Gaster said, lifting the rolls of papers. She wouldn’t have liked the answers to either of those questions, anyway. “But I Need You To Look Over Them For Me.”

Alphys glanced towards the blueprints in surprise. “So soon? Gaster that’s incredible!”

Gaster rubbed at one of the scars along his temple. “I’m Not So Sure. The Plans Are For A Machine. Whether Or Not It’s Implementable Remains To Be Seen.”

“A m-machine?” Her face scrunched in concern. “How l-long would that take to build?”

Gaster merely shook his head in response. “May I Come In? I Need To Sit Down.”

“Oh! O-of course, come in,” Alphys said, stepping aside to make room.

Gaster navigated the cluttered lab out of practice, dropping the plans on the table for Alphys to look over before collapsing into the nearest available chair. Her rooms were just as cluttered as Gaster’s were, overflowing with tools and half completed projects, but Alphys had the added mess of dishes and empty ramen packets that were only ever tidied up when Undyne visited. Her main lab doubled for a living room of sorts, with a mini fridge plugged into the wall, a coffee warmer sitting on top, and a stack of dishes near the lab sink. Her mess had grown out of control even by Gaster’s standards, but he was currently incapable of summoning the energy to care.

“Can I get you something?” Alphys said. He could hear her knocking plates around by the sink. Gaster tipped his chair back so it leaned against the wall, closing his eyes as he reclined. “Some, u-um… soda?”

“No, I’m Fine.” Even if she’d offered coffee he might have passed; his weariness was winning out over his hunger. Perhaps he could catch some rest while Alphys worked. “Just Let Me Know What You Think When You’re Done Looking Over The Plans.”

Alphys made a skeptical grunt, but didn’t push the subject. Gaster let his consciousness drift amid the familiar shuffle and clatter that accompanied Alphys’ presence. The fridge opened and closed, there was a carbonated hiss, and then a scuffing sound as too many dishes were pushed aside to clear some space on the table. Paper rattled as Alphys unrolled the blueprints.

And gasped.

“Gaster.” Her tone was almost a whisper. “Where did you find this?”

Graster cracked an eye open. “I Didn’t Find It Anywhere. I Drew It Up This Morning.” Breathing a quiet sigh, Gaster leaned forward to drop the legs of the chair back to the ground. So much for some rest. “Why Do You Ask?”

“That’s not possible,” Alphys said. “That’s n-not—”

“What?” Gaster stood as Alphys scooped up the blueprints and hurried out of the room. “Alphys, What’s Going On?”

Despite her hurried exit, it wasn’t difficult to track her down. Gaster could hear her rapidly opening and closing filing cabinets in one of her storage closets, muttering nervously to herself as each drawer slammed shut. By the time he stepped in the door she was busy shoving a stack of boxes out of the way to access another cabinet in the back of the room. The blueprints were clutched tightly in her claws, as if she might risk losing them should she relinquish her grip.

“Doctor, What On Earth Has Gotten Into You?” Gaster said, bewildered. He’d never seen his friend so worked up (secret guard-related crushes aside.) “Tell Me What’s Going On.”

“I- I’ve seen these drawings before,” Alphys said, wrenching out another drawer. After one-handedly flipping through its contents, she slammed it shut and pulled open the next. “These e- _exact_ drawings. Where did I put…?”

“Alphys, You’re Not Making Any Sense,” Gaster said, but she wasn’t paying attention.

“Aha! H-here!” Alphys took a step back, drawing a large manilla sleeve out of the cabinet. Edging her way back over to Gaster, she glanced around for a clear surface before settling for the floor. She lay the folder down on the tiles, then flipped the cover open.

Gaster had to look back up and check his plans were still being held by Alphys to confirm there had been no sleight of hand. On the ground, his blueprints lay spread before him. Gaster stared for a long moment, simply trying to process what he was seeing. Wordlessly, he held his hand out for his plans; Alphys reluctantly complied.

Snapping his papers open, he held them out so he could look at them and the ones on the floor at the same time. Surely there were striking similarities, nearly identical sketches of the machine he’d imagined not hours ago, but for them to be the _same_ …

“That’s Not Possible,” Gaster said.

“Th-that’s what I was saying!” Alphys said. “Are you s-sure you didn’t see these drawings s-somewhere before? M-maybe they gave you the i-idea without you remembering?”

No,” Gaster said, bending down to pick up the top sheet of the blueprints Alphys had produced. The paper was aged, thin and wrinkled. Selecting the same sheet from his own drawings, he stacked the papers over one another and held them up to the light. Both monsters stared up at the schematics.

“No,” Gaster repeated after a moment of silence. “I’m _Quite_ Sure This Is No Accidental Reproduction.” Light carved out a silhouette of the page’s writing and figures, backlighting a smattering of equations and the shadow of a machine. The lines of the two papers exactly overlapped one another; a perfect match.

“H- _how_?” Alphys stammered.

“I Don’t Know,” Gaster admitted, dropping the pages back down. Could his temporal powers have something to do with it? No, that couldn’t be it. His time skips only took him back a few minutes at most, and he couldn’t take anything tangible with him. “Where Did You Find These?” Gaster asked, gesturing to the old copies.

“I, I’m not sure,” Alphys said. “There were a lot of old documents left in the lab w-when I became a royal scientist. I j-just stumbled on them one day. Is it… d-do you think… m-maybe this has something to do with your plans for a time machine?”

Gaster hadn’t considered that. “Perhaps,” he frowned. “But It’s Only Plans. I Haven’t Built Anything.”

“Yet,” Alphys added. That sent the two into an unsettled silence. Did the existence of the blueprints imply creating the machine was inevitable? Gaster didn’t like the idea that his actions were predetermined—and especially wasn’t keen on the paradoxes that must arise from having such information. Even if he did recreate the time machine, it didn’t make sense. What purpose did he have in taking these specific documents back? He voiced the thought aloud.

“Why Would I Send Blueprints Back In Time Only To Rediscover Them Now?” he said. “Surely, Finding Them After I Come Up With The Idea Defeats The Point.”

Alphys made a squeaking sound—perhaps a gasp stifled too late. “B-because,” she said, wringing her hands, “because they weren’t for _you_ to discover. They were for _me_. Because if I hadn’t f-found them, I w-wouldn’t have learned all about the n-nature of human and monster souls. And—oh, oh wow—” Alphys looked up at Gaster in dawning awe. “That means I wouldn’t h-have been able to help you when y-you arrived in the Underground. I w-wouldn’t have known how t-to stabilize your soul, and… and… oh, stars, it’s all connected, isn’t it?”

“Alphys,” Gaster said, trying to follow her ramble, “What Are You Talking About?”

Alphys swallowed, her gaze drawn back to the blueprints. “Gaster… there’s something you need to see.”

 

 


	11. Vantablack

**Summary for the Chapter:**

> Here we approach the end.

It was precisely as he designed it. Each specification had been meticulously observed and not a single alteration had been made. Perhaps Alphys hadn’t been confident enough in her understanding of the plans when she built it to risk modifying any aspect of the machine. It was undoubtedly the most complicated device Gaster had ever conceived: nearly a living organism.

The main chassis, reminiscent of a skull, only emphasized that impression. Gaster wasn’t sure what he had been thinking when he gave the machine that form. Perhaps it was because he had been working on the blaster not long before coming up with the design—or maybe the instinct was more deeply ingrained.

The way his plans seemed to have jumped from their pages and into reality in the course of a day was unsettling. But of course, the extractor was much older than that.

“You’re really gunna use it?” Flowey asked. The flower had popped up the moment Alphys left, presumably to give Gaster time to digest everything in peace. He wondered if Flowey was intentionally interrupting that moment.

“I Am,” Gaster said. It was difficult to not linger on the appearance of the extractor, its skull split open to reveal the human-shaped chamber within. The whole contraption seemed to loom over the room, its mass shading much of the area around its base from the lab’s inadequate lighting. Everything about it seemed darker than it should have been. Gaster had to force himself to look away as he began to explore the rest of the area.

“You know it never really worked, right?” Flowey said, following him. “All of Alphys’ tests were failures.”

“And I Suppose You Were There For That?” Gaster guessed. The flower’s silence served as confirmation. Another piece of the puzzle. “Not That It Matters,” Gaster continued. “Alphys Never Used The Machine For Its Intended Purpose.”

“Really?” Flowey perked up. “How’s that?”

Gaster came to one of the room’s doors and opened it; a small office, mostly cleaned out. It would serve.

“From What Aphys Told Me, All Her Experimentations Were Done Using The Souls Of The Deceased Humans,” Gaster said. “However, I Designed The Extractor To Operate On The Living.” He spread his blueprints out over the abandoned desk, setting the old and new plans side by side.

“Dark,” Flowey giggled. “How much will _that_ hurt?”

Gaster didn’t have an answer to that, and was honestly trying not to think about it. _Better than being killed by the king_ , he thought.

 

It didn’t take long for him to familiarize himself with the device. It was strange to be working on a machine he’d designed without actually ever having built it. Alphys was there to answer any questions he had, and when she wasn’t Flowey returned to contribute his commentary. The lab quickly filled with papers and equipment, and it was all too soon that Gaster found himself ready to move forward. Even so, he took an extra day to revisit his notes and prepare a video camera for documentation.

He wasn’t procrastinating. Gaster didn’t procrastinate. He was just being… thorough.

He couldn’t afford for anything to go wrong.

 

“Entry One, Trial One,” Gaster spoke into the video recorder. “Subject Is To Interface With The Extractor In Order To Produce Baseline Readings.”

Apart from the video camera, he and the human were alone in the room. Undyne had reluctantly agreed to wait outside when Gaster had asked for privacy; Alphys had supported Gaster in his insistence on working alone, and for that he was grateful.

This was something he could only do on his own.

The human stood where Undyne had released them and stared at Gaster with hollow eyes.

“If You Don’t Get Inside, I’ll Be Forced To Call Undyne Back,” Gaster said. Their silence was unsettling, and Gaster felt an instinctive urge to fill it. “I Doubt She Will Be As Patient.”

It wasn’t right, seeing a look like that on a face so young. Gaster decided to attribute it to weariness, though if he’d allowed himself to look closer it wouldn’t have been difficult to make out the bruises and cuts the child had sustained since making their trek into the Underground.

Gaster was about to make another threat when the child slowly stepped over to the machine. The extractor was open, vivisected to allow its subject to climb inside. The human hesitated as they stared into the cavern, then glanced back towards Gaster. He tensed, magic instinctively readying for an attack, but the child did not initiate a fight. Perhaps they’d already learned the futility of that.

“Subject Ingressed,” Gaster said as the skull halves hissed shut around the human. “Extraction Machine Coming Online.” Gaster raised a hand and the machine responded, violet circuits of magic tracing over the extractor’s exterior. A hum steadily grew, starting at a whisper and expanding until it reverberated around the room. The two windows that let into the machine began to rattle faintly, but everything held.

“Starting Extraction Procedure,” Gaster said, pulling on his magic and drawing the currents of energy to coalesce in the subject’s chamber. “Ramping Up To Ten Percent Threshold. Power Levels Steady. Current Magic Draw Should Be Sufficient To Bring Out The Human’s Soul.” Sure enough, a yellow light began to trickle through the machine’s windows. Given the extractor’s shape, it appeared eerily reminiscent of two glowing eyes. “After Stage One Is Establish,” Gaster continued, “Further Ramp-Ups Of The Device Will Be Performed. It Will Be Important to Establish The Subject’s Limit Of...”

Gaster paused as a new noise joined the machine’s whine. It was high pitched and stuttering, sharp and piercing. It was a sound so alien to Gaster that even after he realized what it had to be he froze, too stunned to act.

It was the sound of a child screaming.

 

“Entry Number… Entry Number Three.” Gaster paused to compose himself. “Second Attempt At Recalibrating The Extractor. Energy Levels Reduced To One Tenth That Of Baseline Levels. I’m Unsure Further Calibration Will Be Able To Reduce Power To The Extractor While Maintaining Sufficient Energy Levels To Functionally Run The Device. Should This Experiment Prove Equally Traumatic—Stressing, I Mean—Then…” Gaster trailed off. Then what? He would just call the whole thing off? No, that wasn’t an option. “...Then Further Experimentation Will Have To Resume At Baseline Levels, Regardless Of The Subject’s Health.”

Gaster stepped away from the video camera. “Trial Three,” he said, raising a hand towards the Extractor. Once more the machine began to active and draw power towards the central chamber. For a few long moments, only the sound of the extractor’s whir filled the room. Just as Gaster let out a breath, an eery and familiar wail rose from the extractor. Gaster faltered, his hand flinching back and almost severing the magical connection. Grimacing, he straightened his posture and steadied his grip on the device.

Things couldn’t end here. For better or worse… the experiment had to continue.

 

“Entry Number Seven. Summary Of Trials Thus Far.” Gaster sat at his desk, speaking to the camera. The scientist sighed, absently tracing a scar in his skull. “All Six Experiments Have Resulted In The Same Outcome. Despite Varying The Extractor’s Magic Levels, The Interface Causes… Extreme _Physical Duress_ To The Subject. The Damage Can Be Healed After The Extracting Session, But…” A moment of silence passed and Gaster realized he had nothing more to say. With a heavy sigh, the doctor leaned over and turned off the camera. There was no point to this entry. He was just spinning his wheels.

“Watcha up to?” Flowey appeared. _Sensing my frustration, no doubt,_ Gaster thought. Like a shark drawn to blood.

Without responding, Gaster stood and went over to the blueprints, looking over the documents for the hundredth time. He wasn’t sure that changing the machine’s current outputs would be able to mitigate the stress it caused the child. The problem went deeper—a design flaw. And it was far too late to fix things now.

Or was it?

Still staring at the schematics, Gaster summoned a hand construct and sent it to fetch a pencil.

“Been pretty quiet around here recently,” Flowey said. “At least a _day_ since I’ve heard any kids being tortured.”

Gaster was reaching for the pencil his construct had retrieved as the magical hand clenched, snapping the pencil in two. Flowey giggled, and Gaster ground his teeth as he sent the construct off to find another one.

“Enough Of That,” Gaster said. “If You Can’t Stay Civil, Then I Don’t Think You Should Stay. You’ve Been Trying My Patience Enough As It Is.”

“Gosh,” Flowey said as Gaster took up a pen and uncapped it. “I didn't realize I was bothering you. You should have said something!”

Gaster spent a moment seriously considering throwing the pen at Flowey before returning his focus to the blueprints. He wasn’t sure this was a good idea, but ideas were a commodity of which he was rapidly running out. He’d try something small, just to test his hypothesis.

Selecting an empty spot out of the way of the page’s equations and drawings, Gaster drew one quick, small stroke in the margin of his blueprints.

Gaster’s soul lurched, and a deep, disturbing quiver oscillated through his magic. Gaster stumbled as he was caught by a sudden bout of nausea. The sensation passed as rapidly as it had come, but left a faint impression of magical aftershock. A lingering _wrong_ ness.

“Ooooooo!” Flowey giggled. “The timeline _really_ didn’t like that. It kinda tickled. Do it again!”

Gaster shivered, pushing past an aftertaste of disorientation. Moving over to the older, duplicate page of the one he’d marked, he was able make out a smudged but otherwise identical mark to the one he’d just left on his own copy of the blueprints.

Gaster shook his head, trying to clear his mind. He felt like he should have learned something from this test. Confirmed if his hypothesis had worked on not. However, with increasing alarm Gaster realized that he couldn’t recall if the mark had already been there or not. Surely, he’d checked the old copy beforehand. The experiment wouldn’t make sense if he hadn’t checked. Had it simply slipped his mind?

Briefly, Gaster considered duplicating the test while documenting the state of the blueprints beforehand—before quickly thinking better of it. No, continuity was not something he should be playing around with here. Not in this scope, anyway.

If the extrator could not be changed, then he would have to continue working with things as they were.

He would just have to persevere.

 

“G-Gaster.” Alphys stepped into his office. “Um. Hi.”

“Doctor Alphys,” Gaster said, setting aside a tablet of the most recent trial’s schematics. “I Wasn’t Expecting You. Do You Need Something?”

“I, um, j-just wanted to talk,” Alphys said. “If you have a moment?”

“I Can Spare A Few,” Gaster allowed. “I’m Afraid I Don’t Have An Extra Chair To Offer You. I’ve Yet To Migrate Most Of My Equipment Down Here.”

Alphys glanced around the makeshift office. “You know, you d-didn’t have to m-move down here,” she said. “Working r-right next to the extractor can be a little… distracting.”

“Its Presence Doesn’t Bother Me,” Gaster said. “Anyway, It’s More Efficient To Stay Close To My Work.”

“R-right,” Alphys said. Cautiously, she looked up at Gaster. “About your w-work… It’s been almost two weeks, now.”

“Is That What This Is About?” Gaster asked. “Then I Must Apologize. The Process Has Been Taking Longer Than I Expected— A Few Roadblocks I Didn’t Anticipate. If This Is A Problem For The King—”

“No!” Alphys interrupted. “W-well, maybe the king isn’t happy with how long it’s taking—I don’t know—but that’s not the point! I- I’m here as a _friend_ , n-not a scientist.”

“Oh.” Gaster leaned back in his seat, his expression unreadable. “Then What Is It You Want?”

“I... I’m just worried,” Alphys said, hunching down. She appeared to be grow smaller with each word, like a slowly deflating balloon. “This isn’t g-good for you, and I th-think you should stop.”

“Stop?” Gaster frowned. “You Know I Can’t Stop Now. This Work Is Too Important To Abandon. I _Know_ I Can Get The Extractor To Function With A Living Soul. I’m Close.”

“ _Are_ you?” Alphys asked. “You w-won’t tell me anything. And… and the _things_ I sometimes _hear_ … Y-you know, you don’t have to do this alone, Gaster.”

Gaster tried to wave her off. “I Do. I Don’t Expect You To Understand, But I Do.”

Alphys face scrunched in annoyance. “I th-think I _do_ understand. It’s either b-because of my past with the human souls—”

“Don’t Be Absurd,” Gaster, started. “I Would Never Hold That Against You.”

“— _or_ ,” Alphys stressed, “it’s because of _your_ past.”

Gaster looked at her sharply. “Alphys.”

“It is, isn’t it?” she said. “Because of w-where you came from.”

“ _Alphys_.”

“And— and what you were.”

Gaster stood up and Alphys flinched back with a small squeak. Gaster’s look was hard, but he wasn’t meeting her eyes. Breathing in through his nose, Gaster let out a long, controlled exhale.

“My Motives To Continue This Experiment,” he said, speaking each word carefully, “Are _Completely_ Irrelevant To My Past. I’m Sorry You Misunderstood.” Gaster picked up the tablet he had been looking at earlier. “Now If You Would Excuse Me, Doctor, I Should Get Back To Work.”

Alphys didn’t try to stand in his way when he moved to the door, but her disappointment was almost palpable.

“I— I understand lying to everyone else,” Alphys said, following him out his office. “B-but I wish you wouldn’t lie to me. Ever since the b-barrier…” Gaster stiffened, and Alphys didn’t finish her thought. “I just thought y-you’d talk about it sometime. Th-that you’d talk to me.”

“Alphys,” Gaster said, pausing in the hallway, “You’re Practically The _Only_ Person I Talk To.”

“About work,” Alphys agreed. “But not about… all _this_.” She swept an arm around her, taking in all of the labs.

“This _Is_ Work,” Gaster insisted.

Alphys said nothing, but her expression was heartbroken.

After an grey silence that began to stretch, Gaster tapped his tablet. “If There’s Nothing Else To Discuss, Then I Really Do Need To Be Starting The Next Trial.”

Alphys let out a sigh. “Okay. Do w-what you think you have to do. J-just… don’t push yourself too hard. Be _careful_ , Gaster.”

Grimly, Gaster nodded. “I Always Am.”

 

_No, no, no, no, no!_

Vitals crashing. Magic levels unstable, extraction procedure stalled—

Gaster pulled his magic from the machine, forcing it into an emergency stop even as he sprinted across the room to tear the extractor open himself. Dozens of constructs sprang to life as he ran—half of the bones not even shaped into hands—to help pry the machine open faster than the hydraulics were capable. Gaster skidded to a halt by the extractor as something mechanical cracked with a metallic _twang_ and the skull of the extractor split open to reveal the dying child.

Though their screams were still ringing in his ears, Gaster found them no longer moving.

“No, No, Wake Up!” Gaster desperately shook the child’s shoulder. In response, the soul that hovered above their chest gave a weak, fluttering pulse. It was dim—far dimmer than a soul had any right to be. Yellow essence partially illuminated the inside of the extractor, dripping from the ducts that led into the chamber and glowing with a brightness that put the soul to shame. With so much magic lost, the soul was in an extremely fragile state. Gaster needed a healer, fast, but he couldn’t risk removing the child or—

With a faint tinkle of fracturing glass, the soul trembled once, then shattered.

Gaster froze as he was gripped by horror. No, no, this couldn’t be happening—he couldn’t have _lost_ them. The extractor was designed for this. He couldn’t have been this wrong—they couldn’t be _dead_.

Gaster laughed, frantic and unsteady. No, of course, this wasn’t over, he could still fix it. In his panic he had forgotten about his time skips—unthinkable that he had nearly let his emotions get the best of him. Laughter overtook him once more. Not that he thought any of this was funny. _Shock_ , Gaster diagnosed. So much for mind over matter.

Gaster closed his eyes, and the afterimage of the child’s body burned its way into his mind. It was okay. He could fix this. He just needed to clear his mind and concentrate. Two minutes was all he could manage—it should be enough. It _had_ to be.

For the first time in a long time, Gaster activated his magic and felt its tension twist through his bones. There was darkness—the void—and then he was back, aching but whole. His old wounds had had enough time to heal that the time skip didn’t cause his scars to crack or bleed—a small mercy he would have appreciated more in any other circumstance. But here, now…

The child was screaming, and this time Gaster headed their cries. Once more Gaster snapped his magic from the machine, sending it into an emergency shutdown as he hurried to open the extractor.

“It’s Over,” Gaster said, trying to calm them. “Hush, Please, It’s Okay, It’s Over.”

The child was conscious, but not lucid. Their cries didn’t alter as the extracting devices retracted, and they made no sign of hearing Gaster as he tried to calm them down. Only when he touched their shoulder did their cry hitch, pausing for a moment as they gasped for air, before warbling down in a pitiful whimper that soon succumbed to silence. The child’s eyes fluttered closed and their body went slack.

“No,” Gaster said. “No, Not Again.” It didn’t make any sense. He had stopped the extractor at least two minutes earlier than before. They should be okay—it should have been enough _time._

Yet Gaster could only watch as the human slipped into a coma, and the light in their soul faded.

“No, Shit!” Gaster looked frantically around the room for something—anything—that could help him. The extractor held raw quantities of the human’s soul essence but it only operated in one direction, unable to inject the magic back into the child. Could he throw together an IV drip? Use a syringe to inject it directly back into their soul? In its fragile state would it even hold together if he tried?

A Gaster’s mind race, the soul shattered once more.

“Dammit!’ Gaster didn’t have time to waste on thinking. Seizing his magic, he pulled himself into another time skip.

The child was creaming and Gaster shut down the extractor.

Something didn’t seem right. He hadn’t gone back as far as before. Even before Gaster reached the extractor he activated another time skip. Everything reverted a few seconds, but no further.

“Shit, Shit, Shit!” Again Gaster stopped the machine and sprinted to its side. If his suspicions were correct, he couldn’t go back further than his first jump. And if he couldn’t buy the child more time…

No, he couldn’t accept that. This was _his_ experiment— _his_ machine—and _he_ was in control here. There were always options. He just needed to find the right one.

Summoning dozens of constructs to fetch his tools, Gaster took up a needle as he arrived at the extractor and filled it with the yellow magic. As carefully as he could he coaxed the dying soul into the palm of his hand, and pressed the syringe into its surface. Gaster was still in the process of injecting the magic back into the organ when the soul shattered. Without missing a beat, Gaster skipped back in time. He would just have to try again.

So he did. Once more he tried to keep the soul from crashing, and once more it shattered in his hands.

So he tried again.

And again.

And again.

Until eventually he found that _he_ was running low on magic, and each skip pulled tighter along his scars, and each sprint over to the extractor was harder, more impossible, than the last.

Gaster realized it in his soul long before he admitted it to himself. It was over before it had started, and he had lost.

Gaster skipped back one last time. A pair of hand constructs hurried over to his tools as the doctor walked towards the extractor, powering the machine down on the way. His body trembled from exertion as he pushed the chamber’s lid open and reached down to pull out the child. The human whined as they were jostled, and Gaster briefly closed his eyes and took a composing breath. When he opened them his expression was dull and empty.

The hands returned with a glass canister. Using his constructs to unscrew the top, Gaster lifted the yellow soul from the human’s body. The child gave a small shudder at the loss, but remained unconscious. Gaster placed the soul in the canister and clasped the top back on, locking the seal with magic. Once secured, the soul wouldn’t perish even after its owner died. Gaster didn’t move as he waited, the child in his lap and the canister on their chest.

It didn’t take long.

 

Everything was still and quiet. The cold of the extractor’s metal shell indicated some time had passed, but lent no precision to how long Gaster had been sitting there. A blinking red light was the stimulus that finally roused the scientist out of his haze.

Recalling the video camera was still recording, Gaster summoned a construct and sent it across the room to turn the device off. Once that was accomplished the hands returned, and carefully lifted the soul canister out of his lap.

Gaster had not been strong even when he’d had muscles, but even he could manage to carry a small child. They were heavier than he had expected— _deadweight_ , he thought—but it didn’t seem right to carry them with constructs. Gaster slid down the edge of the extractor, stumbling as he landed off balance, then walked to the center of the room. There he stopped, and only stood.

What was he supposed to do? He had never conceived such a scenario. He didn’t know who he should talk to. What he would say. And before that, he didn’t even know what he should do with the child.

 _No,_ he corrected himself. _The body._

He didn’t know what to do.

He didn’t know what to do.

“Wow! So _that’s_ what you’ve been up to.”

Gaster didn’t react as the flower wormed its way up through a crack in the tile floor.

“Golly, I sure was surprised when all those loads started happening,” Flowey said. Gaster wasn’t looking, but he could hear its smile. “I tried to get here when I realized something was going on—wanted to see what all the fuss was about!” The flower giggled, and something cold stirred in Gaster’s soul. “But I lost my progress with each load, of course. Eventually I just waited for you to finish whatever it was you were doing. It wasn’t easy to just wait like that,” Fowey sighed. “But _boy_ , was the wait worth it!”

The cold condensed and sharpened, as if his marrow were turning to shards of ice. Gaster tried to speak but a tension overcame him, and he instead held perfectly, silently still.

“Guess things didn’t go as planned, huh?” the flower said. “Well, that’s okay. Now you’re stronger than you were before. Now you’ve gained some _experience_. Could you feel it when they died?”

The chill was fragile, ready to shatter from the slightest peturbance. Gaster barely dared a breath when he spoke.

“Stop,” he hissed.

Flowey did not stop. “That’s why I stayed friends with you all this time,” he said. “It sure wasn’t easy waiting around to see if something like this would happen, but I knew if I was patient things would pay off. Because when you get down to it,” the flower smiled, “you’re just like me.”

They were just words. They should pass right through him.

“I mean, time magic’s pretty rare!” Flowey continued. “I knew from the start that made you special, just like me. It means we’re privileged. When the rules don’t apply, you get to write your own. And in this world, there’s only one rule I’ve found to be true. Surely you’ve learned it by now?”

Gaster closed his eyes as if it would shut out the noise. He couldn’t focus. Everything was too dull, and cold, and sharp.

“Kill or be killed,” Flowey recited. “And now that you’ve had a taste, why stop here?”

A tremble ran through the ice. “No,” Gaster forced out.

“Why not show everyone what you’re _really_ capable of?” Flowey said. “It’s not as if they wouldn’t _deserve_ it. It was the king that put you into this position, wasn’t it? He’s a _murderer_. He deserves to die. Wouldn’t it be right to kill him, too?”

_“Enough.”_

“And what about Undyne? She’s the one that captured the human,” Flowey said. “She’s _complicit._ You never really liked her much anyway, did you? She was always too observant. If she’d learned the types of things Alphys has… well… Maybe killing her now just prevents the inevitable! And speaking of _Alphys—_ ”

Too far.

The cold snapped, rushing through Gaster in a freezing wave. It was a concentrated fury, stinging and biting at every nerve as it channeled through his magic until he was consumed by it. Disgust roared in his ears while despair prinkled at his vision. His soul was full of so much agony that he could barely keep upright, his sense of self paling before such raw emotion.

It was too much. With a cry Gaster surrendered to his instincts, condensing everything he felt into a magical construct, and releasing it.

The bone speared forward before it had finished forming, stabbing through the flower.

The force of the blow ripped Flowey from the ground and pinned him to the wall. One of his petals fell off as Flowey blinked, letting out a startled laugh.

“Golly.” Dust began to hiss away from the jagged hole in its stem and face. Somehow, it managed to contort its mouth into a final, deranged smile. “Hah. I always knew you had it in you.”

Before Gaster could think to respond, the monster fell away in a pile of dust.

And just like that Gaster was alone once more. The only living soul in a room full of dead. The last of his energy rushed out of him as the construct dissolved, and the scientist sunk to the floor.

 

 

**Notes for the Chapter:**

> If your core trait is perseverance, how do you know when to stop?


	12. Perpetual Motion

**Summary for the Chapter:**

> Alice: How long is forever?  
> The White Rabbit: Sometimes, just one second.

 

What had he done?

Gaster looked from the pile of dust to the body of the child, where the monster and human lay dead at his feet. Was this all he was capable of? Was his legacy to be nothing but pain and death? This wasn’t right. This wasn’t who he wanted to be.

“I’m Sorry,” Gaster said to the child’s body. “I Don’t Know What To Do. This All Went So Wrong So Fast, And I Was Only Trying To Help.” Gaster’s voice cracked with the last word, and he fell silent. The scientist traced an aching scar across his skull before speaking again. “I Should Have Done Better. I Know It’s Meaningless Now, But I’ll Try To Atone. Somehow. You Didn’t Deserve This. _Nobody_ Deserves This.” Gaster sighed, and the exhale turned into a pained, breathy laugh. “I Suppose That Answers What I Need To Do Next.”

It certainly wasn’t something he _wanted_ to do. Did that make him a bad person? Gaster had never been particularly good at being good.

Regardless of what he wanted, this was something he had to do. If he could prevent even a little of the harm he had caused…

Gaster summoned his magic, bowing beneath the weight of exhaustion as he gathered his dwindling energy. Sparing a few more seconds to make sure he was giving himself enough time, Gaster loosed the magic and skipped back in time one last time.

“You— oh.”

Flowey looked around in surprise.

“You brought me back?”

Gaster staggered a step forward as the weight of the child returned to his arms and briefly threw off his balance. Kneeling down, Gaster carefully set the child’s body on the ground. Only once they were tended to did he look at Flowey.

“I Didn’t Want To Bring You Back,” he said.

Flowey frowned. “I don’t understand. Then why do it?”

Gaster sighed as he straightened back up. “Because As Little As I Like You, I’m Not A Killer.”

“Hah!” The flower sneered, jabbing a vine in the child’s direction. “That ship has already sailed, friend.”

Ugliness stewed in Gaster’s soul.

“Flowey,” the doctor said, “I Want To Make This As Clear As Possible. We Are Not Friends.”

“Hehe.” Flowey shook his head. “Yeah. I guess we’re really not. You know, I have to say I’m disappointed. I expected more from you. At the end of the day you just couldn’t follow through. It’s pathetic, really.”

Gaster didn’t react to Flowey’s spite, but felt a wisp of his previous anger curl through him. “If You’d Rather I Left You Dead, You Are Making A Compelling Argument.”

Flowey scoffed. “ _Please_. You’ve shown your true colors. You’re a _coward,_ just like the rest of them. Just another monster that’s wasted my time.” The flower’s mouth curled cruelly. “I guess that means I can stop holding back now.”

Gaster braced himself, practically able to taste the malicious intent that was rolling from the flower in thick waves. Though he had used a significant portion of his magic on his repeated attempts to save the child, he still had more than enough to put up a fight.

“I Won’t Bring You Back Again,” Gaster warned. “You Only Got One Second Chance.”

Flowey erupted into a fit of giggles. “A second chance? That’s one more than I’ll be giving you! It’s about time I figured out how to get my control of the timeline back, don’t you think? Golly, it’s going to be _fun_ learning how to kill you. _Permanently_.”

Perhaps, Gaster wearily considered, choosing mercy had been a mistake.

Gaster summoned a bone construct, and this time Flowey didn’t give him a chance to use it. Moving with a speed he’d rarely seen the flower display, Flowey darted back to his crevice with a giddy laugh.

“See you around, buddy!” he called, and then the flower was gone.

It was several minutes before Gaster allowed his magic to dissipate. He’d made an enemy today, though perhaps that act had merely been overdue. The flower wasn’t strong, but Gaster didn’t doubt it was capable of following through with its threat. The thought should fill him with dread, he reasoned, but looking down at the child he felt only emptiness.

“Fuck.”

The word was spoken in one hollow, monotonic syllable. It seemed an accurate summary of the day’s events. There was something about the word’s staccato that felt angry and cathartic. Gaster tried it out again.

“ _Fuck._ ”

This time, he _was_ angry. What sort of world was this where the innocent died and those deserving of death were the only ones he could save? He looked down at the dead child.

“Fuck This.”

He looked over at the door to his office.

“Fuck Everything.”

An idea slowly began to take shape as he started toward his office. Gaster left the child’s body on the ground—disrespectful, perhaps, but inconsequential. It didn’t matter what happened to them now. He had a plan.

A really, really terrible plan. But, seeing as how all of his good plans had failed, maybe that’s what it would take.

“Fuck Me,” Gaster sighed, pushing open the door and wading through his office until he stood before the extractor blueprints. He found the two copies of the plans side by side, but turned his attention to only one of them.  

Perhaps it was his imagination, but it almost seemed as if the world tremored when Gaster lifted the newer set of blueprints from his workstation. He had not forgotten the quake in spacetime that had accompanied his last tampering with the papers—in fact, he was counting on it.

Flowey had said something about disrupting the timeline. Gaster’s mouth pulled into a bitter smile. What did a flower know of general relativity?

“Fuck The Timeline,” Gaster said, and his hands tensed to rip the blueprints in half.

But he never got the chance.

This time it wasn’t a ripple, but a roar. A concussive wave tore through room, and spacetime distorted about the aberration. Time stretched, the office convulsed, and in the instant that preceded Gaster’s movement—as if the very universe comprehended his intention to rip the plans to shreds—everything simply _stopped_.

Darkness.

Gaster gasped at its suddenness, disoriented and abruptly smothered in an overwhelming sense of _deja vu._ He didn’t understand what was happening, yet it was familiar. He was nowhere, without sight or sound or touch, yet…

“Right On Time,” a voice said. Gaster knew that voice. He knew this place. It was slow to come to him, but he’d been here before. He’d met someone.

The voice chuckled. “That Was A Joke, You See? Because Time Is Meaningless Here. You’re Only ‘On Time’ Because It Has To Be Now. No?” The voice sighed. “Sans Would Have Got It.”

Gaster remember how to speak. _“Sans?”_ The void memories were seeping back into him, slow and reluctant. Gaster raised a hand to his head, willing the fog to clear. _“You’re… Me.”_

“It Will All Come Back Presently,” the other Gaster assured him. “It Just Takes Some Time.” There was an expectant pause, and Gaster realized a beat too late that had been another joke. The other sighed. “Well, That’s To Be Expected, I Suppose. Do You Realize How Very Rash You’ve Just Been?”

Gaster was still attempting to process his thoughts. He could at once recall meeting and forgetting this other self before. _Several_ times before. But those versions were different from this one—-literally, he realized. Gaster tried to focus on his other self, but couldn’t quite discern their physical shape. There was a shadow in the darkness, a sense of something existing in the black, but that was all and nothing more. They hardly seemed to be there at all.

Another pause had elapsed by the time Gaster realized the other had asked him a question.

 _“Sorry,”_ he said. _“I’m Still Trying To Adjust. What Was Rash?”_

“I Can’t Believe I Even Have To Explain This,” the other said, “But Actively _Trying_ To Create A Paradox Is Generally Considered A Bad Idea.”

 _“Oh,”_ Gaster said. _“Yes, I Suppose It Was. But The Child… I Couldn’t Think Of Any Other Way…”_

“There Was Nothing You Could Have Done,” the other said, emanating distant pity. “It Has Always Happened That Way.”

 _“Predestination,”_ Gaster noted. At the same time, he tried to get a better bearing on his surroundings. If he concentrated he could begin to give himself a form, which was greatly preferable to existing as a nebulous void. His soul was the first part of his self to appear, with everything else slowly beginning to fade in after, like shadows on a developing film. _“Alphys Said Something About Predetermination When I First Made The Blueprints. But It Can’t All Be Set, Can It? You’re Asking Me To Abandoned To Notion Of Free Will.”_

The other hesitated. “Yes And No,” it said presently. “Perhaps, For Others, Free Will Does Exist. I Can Only Speak To Our Experience. When Was The Last Time You Brushed Up On Your Quantum Mechanics?”

Gaster grimaced, to the great amusement of the other.

“That Was A Trick Question,” it said. “We Both Know You Haven’t Studies That Since Before We Came To The Underground. But I’ve Had A Lot Of Time To Consider It, Lately. Recall The Uncertainty Principle.”

Gaster did. _“The Relation Between A Particle’s Position And Momentum, And The Extent To Which You Can Know The Precision Of Either. I Don’t See How That Is Relevant.”_

“Quantum Particles Exist In A Range Of States With Varying Levels Of Probability,” the other said. “That Is To Say, There Are Many Potential States A Particle Could Be In… Until It Is Observed.”

 _“Which Causes The Function To Collapse,”_ Gaster continued. _“Then The Particle Is Only Observed In A Single State. I Think I See Where You’re Going With This.”_

“When I Became Removed From The Timeline, I Ceased To Interact With Time Linearly,” the other said. “Past, Present, Future—These Are All Concepts That Begin To Lose Meaning When Every Moment Exists Simultaneously. Of Course, Becoming Aware Of My Own Timeline Meant I Was Capable Of Observing Everything That I Have Done—And Will Do. It Is This Knowledge That Inherently Prevents Me From Altering It. I Suppose You Could Say Becoming Removed From Continuity Caused All My Potential Timelines Collapsed Into A Single Series Of Events.”

 _“Stars,”_ Gaster said. How was he supposed to react to that? His first instinct was to dismiss the theory entirely, but considering the source… _“Then, Even This Conversation?”_

“Oh Yes,” the other said. “I Recall All This Happening Before. It’s A Rather Strange Sensation To Become Accustomed To, Knowing What I Will Say Before I Speak, What I Will Become Before I Become It. Existing In The Void Has Been A Very Rocky Transition.”

Gaster still wasn’t convinced of the inevitability of his fate, but found the idea of pursuing the conversation any further to be equally disagreeable. The line of thinking made him uneasy, and he opted to instead change the subject.

 _“You’re More Rational Than The Other Versions I’ve Met Here Before,”_ Gaster said. _“Some Of Them Were…”_ Gaster faltered when he couldn’t find a delicate way of wording it.

“Unstable?” the other suggested. “Unfortunate, But True. I Guess You Could Say That Out Of All The Versions Of Ourself You Meet While In This Place, I Am The Version That’s Closest To You. It’s Not Been Long Since I Fell Into This Place, And I’ve Not Yet Entirely Adjusted To Existence Here—As Is Evidence, No Doubt, In My Inability To Give Myself Form.” The darkness implied the impression of a helpless shrug. “Creating Shape With Negligible Magic And A Fractured Soul Is A Trick For My Later Versions To Discover. However This Version Of Me Is The First Version To Interact With A Past Self—And It’s Quite Stimulating, I Must Say! I Can’t Blame The Older Versions For Interfering So Much When There’s So Very Little To Do And Timeless Moments To Fill. No Small Wonder Why Our Sanity Eventually Takes A Hit.” The other let out a small sigh of disappointment.

The candid manner with which the other spoke of their inevitable decline left Gaster feeling disturbed. _“There Really Is Nothing That Can Be Done To Avoid This?”_

“I Am Afraid Not,” the other said, emanating sympathy. “Even This Conversation Is An Act Of Futility, Given Your Inability To Be Aware Of—And Change—Your Fate. Memories Formed In The Void Cannot Persist In Normal Spacetime, As You Are Aware. However, I Think It Is Better For Us That Way. To Meet Our Fate Blindly—To Have Chosen It, Rather Than Felt Bound To It—Is What Gave Our End Meaning.”

Gaster didn’t understand how choosing a fate could make it meaningful. Rationally speaking, it was the act rather than the intent that impacted others. Once more this version of himself seem foreign to Gaster, as if he were talking to someone he hardly knew. Instead of debating the matter, however, Gaster shook his head.

 _“How Did You End Up Here?”_ he asked.

“Ah.” The other’s focus seemed to grow distant, and they felt both sad and faintly proud. “Or How Will You End Up Here, I Suppose You’d Like To Know. I Must Apologize, But Today Is Not The Day You Learn That Story. My Ability To Maintain This Conversation Is Not Inexhaustible, While That Story Is Long, And There Is Still Work To Do. However,” the other added, “I May Tell You This. The Reason For Our Exile To This Dimension Is Due To Self Sacrifice—Perhaps The Only Selfless Act We Ever Achieved In Our Life.”

Gaster didn’t know how to feel about that. Should he also feel proud he’d done something right in the end? It was hard not to way that against the knowledge that it would cause him to end up here.

 _“Was It Worth It?”_ Gaster asked.

“Worth It?” The other laughed softly. “Even Now Knowing The Fate That Awaited Us, If I Were Given The Opportunity Redo My Last Moments I Would Make The Same Choice Without Hesitation.”

Gaster tried to fathom what might be important enough that choosing timeless, formless oblivion seemed the better option. Would he go so far to bring the human child back? He’d done everything in his power to save them, but… No, Gaster realized with disappointment. He wouldn’t even sacrifice himself for that.

 _“I’m Afraid I Can’t Understand,”_ he said.

“You Couldn’t,” the other agreed. “It’s Something You Can Only Experience, And You Still Have Much Growing To Do.”

Gaster frowned. _“Forgive Me For Saying, But That Sounds Rather… Irrational.”_

“It Is, Isn’t It?” The other said, merely laughing it off. “Now, The Time For Pleasantries Is Over. Are You Ready To Lend Me Your Strength?”

An instinctive part of Gaster pulled away at the question, as curious as he was wary. Previous encounters with his future selves had not all been so cordial, and Gaster was beginning to understand that his visits here were often orchestrated to some dubious purpose or another.

The other noticed his hesitation. “How Sad Is It That We Cannot Even Trust Ourself?” They sighed. “As I’ve Said, I Am Still Weak And Unadjusted To Existence Here. I’ve Yet To Gather All The Scattered Fragments Of My Soul And Reshape What Is Gone From Nothingness; My Strength Is Limited And I Can Only Act With Your Magic, Given Freely.”

 _“To What End Will You Be Using It?”_ Gaster asked.

“To Ensure Continuity,” the other said, gesturing to something Gaster held. Looking down, Gaster found the blueprints in his grasp, clutched tightly in the same gesture he’d held them in when he’d intended to tear the plans apart. Now he relaxed his grasp, wondering how the papers had been brought with him.

“They Must Be Placed Back In Time For Alphys To Find Them,” the other said, “So That Everything Happens As It Should.”

 _“So That The Extractor Is Built,”_ Gaster said, following the other’s line of logic, _“And I Use It On The Child, And They Die. That’s Not A Very Compelling Argument.”_

“You Can’t Change It,” the other insisted.

 _“I Could Chose Not To Help You,”_ Gaster said. _“I Could Refuse To Take The Blueprints Back.”_

“But That Is Not The Decision You Make,” the other said, “And It Is Not A Decision At All. I Am Simply Telling You What Will Happen—What Has Happened—What Will Always Happen. Our Time Is Set.” The other rippled with exasperation. “But Let Us Pursue This Theoretical, If You So Insist. The Blueprints Never Arrive In Alphys’ Lab; She Never Builds The Extractor Or Learns About Soul Magic. Flowey Is Never Created. You Arrive In The Underground, And Die Without Her Specialized Care. Later, When Papyrus And Sans Arrive In The Underground—”

 _“They’re Alive?”_ Gaster interrupted. _“They’re Here? In The Underground?”_

“Not Yet,” the other said. “We’re Getting Off Topic. Suffice To Say, Without Alphys’ Dappling In Soul Magic, Years From Now The Underground Will Never Be Freed. I Can Only Speculate At What Might Become Of This Place When The Seventh Human Fails To Free Everyone, But It Is Unlikely To Be A Place Full Of Hope.”

 _“But Sans And Papyrus,”_ Gaster said. _“They’re Well? They Survived The Passage To This World?”_

“Our Priorities: Skewed, As Always,” the other noted. “Yes, They Survive. In Fact You’re Fated To Reunite With Them In Your Not-So-Distant Future. Although,” the other added, “That Is Only Assuming We Deal With The Blueprints Properly.”

Gaster hesitated.

“Oh Please,” the other said. “You’d Rather Stay Here And Prove A Point Than Do What Is Needed? Is Trying To Disrupt Our Fate Really So Important?”

 _“Perhaps,”_ Gaster said. _“I Would Rather Try To Change It Than Do Nothing.”_

“Yet You’re Trying To Change It By _Doing_ Nothing,” the other pointed out. “Perhaps, Out Of Curiosity, A Different Me With More Soul And Less Knowledge Would Let You—But It Is Not Just Our Fate That Would Be Affected By This. The Underground Needs You. Alphys Needs You. Sans And Papyrus Will Need You… Especially Sans.”

 _“Sans Is Resourceful,”_ Gaster said, but his protest sounded half hearted even to himself. The years had dimmed his remorse over losing those two, but he still keenly felt guilt and responsibility for their fates. And now to learn they might have survived after all…

“You Owe It To Them To Be There When They Arrive,” the other said, “And You Owe It To Yourself To Move On.”

Gaster was silent for a long moment before he let out a sigh. _“What Do You Need Me To Do?”_

“Lend Me Your Magic,” the other said, drifting closer. Despite their proximity—if concepts like distance could even exist in such a space—Gaster gleaned no clearer impression of the other’s form. “Offer It Willingly And I Will Be Able To Use It. It Won’t Take Much—Here, Look.”

Something shimmered in the darkness. Gaster concentrated on the image, distantly recalling having witnessed something like this before, and as if reacting to his will the light faded into a scene. The room it showed was dark, but compared to the void it might as well have been daylight: an unfamiliar office with old papers and discarded officeware. Nothing much to look at, though Gaster still found it curious.

_“This Is A Scene Of The Past?”_

“Yes,” the other said, “From Before Your Time, And Even Alphys’. But This Is Where She Will Find The Plans To The Extractor. All That Needs To Be Done Now Is To Put Them There.”

Gaster looked down, but the plans were no longer in his hands; the other held them.

 _“You Couldn’t Do This Yourself?”_ Gaster asked.

“My Ability To Interact With The Timeline Is Limited,” the other said. “And At This Moment, Impossible Without Your Magic. Speaking Of…?”

Gaster gave a curt nod. Reaching for his magic Gaster found it, muted by the void, but there nonetheless. His soul began to glow as he gave form to his magic, then—reluctantly—offered it to the other. They accepted with extreme care, though Gaster still shivered from the way it linked himself to the entity that was at once so familiar and so foreign, feeding glimpses of intent that were as reassuring as they were disquieting. The other breathed a sigh of relief as they connected with the magic, and for a frightening moment Gaster thought it had been a mistake to give them a taste of what they’d lost. The fear passed, however, as the other turned at once to their work.

The image of the office sharpened. No longer like a screen, it seemed to Gaster as if the room stood open before him, and he might tip and fall into it if he were not careful. The other held the blueprints before him, and reached out to the dusty room. For a moment the plans curled back, as if repelled by a light breeze. Then the resistance ceased and the papers passed back out into the timeline, ensuring their continuity. And for the briefest moment, as the other pushed the blueprints into reality, their formless grasp took form and the shape of bones they had once possessed appeared around the blueprints in transparent, dull whisps. The hand persisted as it was drawn back into the void, and Gaster could feel the other examining its new appendage with vague curiosity and nostalgia. When the other released Gaster’s magic, the hand vanished back into nothingness.

Gaster slumped, shamefully relieved to have his magic back fully under his own control. The other, if they were aware of this relief, did not bring attention to it.

 _“So That’s It?”_ Gaster asked. Already the image of the past was beginning to fade. _“That’s All We Needed To Do?”_

“That’s It,” the other confirmed. “And Now I Will Let You Return To Your Time. I Suppose I Should Wish You Luck, Though Considering The Circumstances That Would Be Somewhat Meaningless.”

 _“And Here I Thought You Were Worried It Would Sound Too Sentimental,”_ Gaster teased.

“Perhaps You Could Benefit From More Of That,” the other said. “Too Often We’ve Allowed Our Drive To Blind Us. You Could Afford To Learn A Thing Or Two From Sans And Papyrus.”

Gaster was skeptical. _“Even Papyrus?”_

“Especially Papyrus,” the other said. “But You’ll Soon See For Yourself. Farewell For Now.” Gaster could feel the other bloom with sudden and smug amusement. “See You In The Past.”

Gaster started to respond, but the other had let go and already he could feel the void and his void memories receding, his soul pulling him back to his own space and time. It pulled him back to the extractor, back to the dead child and a new enemy. It pulled him back to his sorrow and regret and frustration.

But even as it cast him back into the world—blinking away the sensation of forgotten thoughts and wondering, for just a moment, what it was he had been doing in his office—it left him with newly forged determination.

Despite everything, Gaster wasn’t ready to give up. It was his nature, of course, to persevere. But now he would do so with a purpose, a burning desire to fix what he had done wrong, and ensure, at the very least, he would not repeat his mistakes again.

 

Work on the time machine started up once more. This time, however, Gaster treated its development as a hobby, and even invited Alphys to consult on several aspects of its construction. Apart from his personal projects, his day-to-day activities largely concerned the development of the Core and management of the Hotland Labs. In fact, his new dedication to the Underground became his primary focus, and by the time he finally completed the time machine, one ordinary afternoon, he realized he could not—would not—activate it. There was nothing for him to go back to.

This was his home.

 

Days blurred into weeks blurred into months as his projects grew to fruition. Under Gaster’s care the Core came to provide electricity to ninety-five percent of the Underground, and the intranet—previously only available to the laboratory’s staff—became a cavern-wide hit. In anticipation of future confrontations with humans, he and Alphys set up a plethora of cameras and anomalous-magic detectors from Snowdin to New Home. The next time a human fell Gaster would be ready. It was with equal amounts of dread and resolve that he prepared for that inevitability. There would be no mercy—and no cruelty—shown that day. With luck, it could be over before anyone got hurt. The needs of the many, Gaster had come to believe, outweighed the needs of the one.

Gaster was in his office, burning through a steep pile of paperwork, when the alarm finally came. A magical aberration, Alphys reported, though not matching any of the magical frequencies found in the human souls. Still, the event was out of the ordinary and warranted a look, so Undyne had left to investigate.

“Doctor Gaster.” The Captain stepped in the door at the same time she knocked, not waiting for his reply. Over the years the two had developed a strained but professional relationship, held together largely by Alphys’ willpower.

Gaster spared Undyne a quick glance before returning to his work. He was more than capable of multitasking, and it was clear from the lack of urgency that the source of the magic had not, in fact, been a human.

“Reporting back from Snowdin,” Undyne said. “No luck finding any humans, yet.”

“Yet?” Gaster repeated. Snapping his fingers, a set of hand constructs appeared to fetch the next stack of project proposals, and made a point of russling some of the pages on the way back. If she hadn’t completed her search, why had she bothered coming back to report in?

“We hadn’t finished sweeping the area,” Undyne admitted.

Yes, Gaster had gathered that much. “Well If That’s All, Then I Am Quite Busy,” he said, gesturing for the Captain to be off. “Let Me Know If You Find Anything Else.”

“Actually,” she said, “that’s why I’m here. We didn’t find any humans, but these skeletons said they might-”

_“What?”_

Gaster’s head jerked up, and for the first time since Undyne had entered Gaster realized she was not alone. Two skeletons stood beside her, one short and mellow, the other tall and tense. The first wore a wide grin; one that seemed carefree, to the unfamiliar eye, as opposed to the uncertainty it masked. The tall skeleton, on the other had, was making no attempt to hide his own confusion. Gaster had never seen either before in his life, but he knew with certainty, with _absolute_ certainty…

“Stars,” Gaster breathed, hardly aware he was standing up. His mind raced as he searched for an explanation and found one, curiously quick, as if his subconscious had been waiting all these years for him to understand what had happened. It was with an almost dreamlike quality that all the pieces fit together, and for a moment Gaster believed it _was_ a dream, playing a cruel trick on him. To break himself out of this spell Gaster looked between the two skeletons, and forced himself to speak around the abrupt tightness that had formed in his chest.

“Is It… Is It Really You?” he asked.

The small skeleton’s smile turned genuine, and he huffed out a weak laugh.

“hey, doc,” Sans said, and with those words Gaster knew it was no dream, no trick, and that his lost friends had returned.

 

 

 

**Notes for the Chapter:**

> One year and 108,000 words later, Undertale Beginnings is finished. 
> 
>  
> 
> Thanks for reading.


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